,.  ~4  UNWERSiny  CALIFORNIA 
,1  COLLEGE  of  MINING 

|/  |        DEPARTMENTAL 
LIBRARY 


BEQUEST  OF 


SAMUELBENEDICTCHRISTY 

PROFESSOR  OP 

MINING  AND   METALLURGY 
1885-1914 


QUANTITATIVE  ANALYSIS 


FOR 


MINING  ENGINEERS 


BY 


EDMUND    H.  MILLER,  PH.D. 

ADJUNCT  PROFESSOR  OF  ANALYTICAL  CHEMISTRY  AND  ASSAYING 
IN  COLUMBIA  UNIVERSITY 


NEW  YORK  : 

D.    VAN    NOSTRAND    COMPANY 

23  Murray  and  27  Warren  Streets 

1904 


Entered  according  to  Act  of  Congress,  in  the  year  1904,  by 

EDMUND  H.  MILLER 
In  the  office  of  the  Librarian  of  Congress,  at  Washington,  D    C. 


PRESS  or 

THE  NEW  ERA  PRINTING  COMPANY, 
LANCASTER.  PA. 


PREFACE. 


This  small  book  on  quantitative  analysis  consists  entirely  of  a 
series  of  articles  which  appeared  in  the  SCHOOL  OF  MINES  QUAR- 
TERLY, Volume  XXV.  It  was  written  primarily,  to  furnish  the 
engineering  students  at  Columbia  University,  particularly  the  min- 
ing engineers,  with  the  directions  required  for  their  course  in 
quantitative  analysis.  Also,  as  so  many  men  now  enter  the  min- 
ing course  with  advanced  standing  from  other  universities,  col- 
leges and  schools,  it  seemed  advisable  to  show  in  this  way  what 
we  require  from  our  mining  students  in  quantitative  work. 

No  attempt  is  made  to  cover  the  entire  field  of  inorganic 
analysis  ;  but  a  few  important  analyses  are  given  in  considerable 
detail ;  the  aim  being  to  describe  these  analyses  with  enough 
explanation  for  the  student  to  work  understandingly  and  with  an 
appreciation  of  the  modern  theories  of  chemistry.  References  will 
be  found  at  the  end  of  the  chapters  to  books  and  articles  giving 
additional  information  on  the  subjects  treated  ;  and  the  last  chapter 
is  devoted  entirely  to  references  on  important  analyses  which  are 
not  given  in  the  text  or  required  in  the  course  for  mining 
engineers. 

In  describing  some  well-known  methods,  it  is  not  always  pos- 
sible to  give  to  each  chemist  exactly  the  credit  he  deserves  in  its 
development,  so  acknowledgment  is  made  here  to  all  the  stand- 
ard books  on  the  subject,  and  special  references  are  made  to  the 
more  recent  journal  articles.  The  methods  as  described  in  many 
cases  embody  the  results  of  investigations,  which  have  been  car- 
ried out  in  the  Havemeyer  laboratories  by  the  recent  graduates  in 
chemistry.  Acknowledgment  is  made  to  this  work  and  also  to 
Dr.  Morgan,  Dr.  Sherman  and  Dr.  Joiiet  for  helpful  suggestions 
and  corrections. 

E.  H.  M. 

QUANTITATIVE  LABORATORY, 

COLUMBIA  UNIVERITY,  Dec.  31,  1903. 


in 


TABLE  OF  CONTENTS. 


CHAPTER   I. 

PAGE. 

lONIZATION I 

Cations,  Anions 3 

CHAPTER   II. 

MASS  ACTION 7 

Effects  of  Mass  Action  on  lonization 9 

Mass  Action  on  Indicators II 

Solubility  Product 13 

Complex  Ions 15 

CHAPTER    III. 

THE    ANALYSIS    OF   MAGNESIUM  SULPHATE    AND    THE   DETERMINATION   OF 

ALUMINA  IN  ALUM 16 

Crystallized  Magnesium  Sulphate 16 

Determination  of  Water 16 

Determination  of  Sulphuric  Anhydride 17 

Properties  of  Barium  Sulphate 18 

Determination  of  Magnesia 20 

Properties  of  Magnesium  Ammonium  Phosphate 21 

Potassium  Alum  22 

Determination  of  Alumina 22 

Properties  of  Aluminum  Hydroxide  23 

CHAPTER    IV. 

COAL  ANALYSIS 25 

Sampling 25 

Proximate  Analysis 26 

Determination  of  Sulphur 27 

CHAPTER  V. 

FERRIC  AMMONIUM  ALUM 30 

Determination  of  Ferric  Oxide  Gravimetrically 30 

Determination  of  Ferric  Oxide  Volumetrically 32 

By  Potassium  Permanganate 32 

By  Potassium  Dichromate 37 

CHAPTER  VI. 
ANALYSIS  OF  IRON  ORE. 

Determination  of  Iron 39 

Scheme  for  the  Determination  of  Silica,  Sulphur  and  Phosphorus  in  one 

portion 42 


vi  CONTENTS. 

Notes,  Reasons  and  Properties  of  Precipitates 44 

Additional  References 47 

CHAPTER   VII. 

PIG  IRON  AND  STEEL  ANALYSIS 48 

Determination  of  Phosphorus 48 

Carbon  Determinations 50 

Sulphur  Determination 53 

Oxidation  Methods 53 

Evolution  Method..  55 

Silicon  Determination 56 

Determination  of  Manganese 57 

Additional  References , 57 

CHAPTER  VIII. 

DETERMINATION  OF  MANGANESE  IN  SPIEGEL  AND  IN  MANGANESE  ORES. 

Volhard's  Method 59 

Chlorate  Separation 61 

Gravimetric  Method  for  Spiegel 61 

Notes  on  the  "  Basic  Acetate"  Separation 62 

Removal  of  Nickel  and  Cobalt 64 

Precipitation  of  Manganese  by  Bromine 64 

Precipitation  of  Manganese  as  Phosphate ...  65 

Additional  References 66 

CHAPTER   IX. 

DETERMINATION  OF  ZINC  IN  ORES 67 

Volumetric  Method  by  Potassium  Ferrocyanide 67 

Method  for  Franklinite , 71 

Gravimetric  Method 7 2 

Precipitation  of  Zinc  as  Sulphide 72 

Precipitation  of  Zinc  Ammonium  Phosphate 73 

Additional  References 74 

CHAPTER  X. 

LIMESTONE  ANALYSIS 75 

Determination  of  Silica  and  Oxides  of  Iron  and  Aluminum 75 

Precipitation  of  Calcium  Oxalate 77 

Magnesium  Determination 79 

Effect  of  Barium  Manganese  or  Phosphoric  Acid 80 

Applications  of  the  "  Limestone  "  Analysis 8l 

Determinations  of  Carbon  Dioxide,  Sulphur  and  Phosphorus 82 

CHAPTER    XI. 

THE  DETERMINATION  OF  COPPER  IN  ORES  AND  MATTES 84 

Electrolytic  Method 85 

Iodide  Method 90 

Potassium  Cyanide  Method 93 

Thiocyanate  Method 95 


CONTENTS.  vii 

CHAPTER    XII. 

THE  DETERMINATION  OF  LEAD  TN  ORES 97 

Gravimetric  as  Lead  Sulphate 97 

Ferrocyanide  Method 99 

Molybdate  Method 101 

CHAPTER    XIII. 

THE  DETERMINATION  OF  ANTIMONY  IN  ORES 103 

Gravimetric  Method 103 

Volumetric  Methods 106 

Weller's  Method 106 

Mohr's  Method 108 

CHAPTER   XIV. 

THE  DETERMINATION  OF  ARSENIC  IN  ORES no 

Distillation  Method no 

Precipitation  of  Magnesium  Ammonium  Arsenate 112 

Separations  of  Arsenic  and  Antimony  112 

Volumetric  Methods 113 

Pearce's  Method  as  Modified  by  Bennet  l?3 

Sodium  Peroxide  Method 115 

Additional  References  to  both  Arsenic  and  Antimony 117 

CHAPTER   XV. 

SLAG  ANALYSIS 118 

Iron  and  Manganese  Slags 119 

Lead  and  Copper  Slags 121 

CHAPTER    XVI. 

FLUE  GAS  ANALYSIS 125 

Reagents  126 

Sampling 128 

Analysis 128 

Results 129 

CHAPTER    XVII. 
REFERENCES  TO  ADDITIONAL  ANALYSES 131 


NOTES  ON  QUANTITATIVE  ANALYSIS 
FOR  MINING  ENGINEERS. 

CHAPTER  I. 

lonization. 

Chemistry  to-day  must  consider,  besides  atoms  and  molecules, 
ions.  Ion  was  the  name  given  by  Faraday  to  the  moving  par- 
ticles in  a  solution  which  carried  the  electric  current.  Many  years 
later,  in  1887,  Arrhenius,  in  attempting  to  explain  the  abnormally 
high  osmotic  pressures  given  by  many  Aqueous  solutions,  discov- 
ered that  only  those  solutions  which  conducted  the  current  gave 
these  high  osmotic  pressures,  and  so  decided  fhat  there  were  pres- 
ent in  such  solutions  particles  other  than  mMecules,  which  he 
designated  by  Faraday's  name  of  ions. 

Although  there  is  now  abundant  evidence  of  t,.e  existence  of 
ions,  a  few  words  on  osmotic  pressure  may  not  be  out  of  place,  as 
it  affords  one  of  the  most  convincing  proofs  of  ionization.  It  has 
been  shown  by  experiment  that  the  laws  of  gases  in  regard  to 
pressure  and  temperature  apply  equally  to  substances  in  solution. 
Here  the  volume  is  the  volume  of  the  solution,  and  the  pressure  is 
not  exerted,  as  in  the  case  of  gases,  on  the  walls  of  the  containing 
vessel;  but  requires  for  its  detection  a  semi-permeable  membrane 
of  such  a  nature  that  the  solvent  can  pass  through,  but  the  dis- 
solved substance  cannot.  Such  diaphragms  were  made  by  Pfeffer 
in  1877,  and  with  them  he  showed  that  the  osmotic  pressure  of 
such  substances  as  sugar  obeyed  the  gas  laws ;  that  doubling  the 
number  of  molecules  of  sugar,  dissolved  in  a  given  volume  of  water, 
doubled  the  osmotic  pressure,  and  also  that  increasing  the  tem- 
perature increased  the  pressure  in  the  same  ratio  as  for  gaseous 
molecules. 

This  important  agreement  having  been  shown  for  a  number  of 
substances,  usually  organic,  it  was  found  that  there  were  many  salts 
and  other  inorganic  compounds,  such  as  acids  and  bases,  which  did 
not  obey  the  law,  but  which  gave  osmotic  pressures  greater  than 


2  QUANTITATIVE   ANALYSIS. 

those  calculated  from  the  number  of  molecules  present,  so  that,  as 
the  pressure  depended  on  the  number  of  particles,  there  must  be 
more  particles  than  molecules  present.  This  gave  rise  to  the  theory 
of  ionization  or  electrolytic  dissociation  which  is:  that  many  com- 
pounds, such  as  salts,  when  they  are  dissolved  in  water  are  disso- 
ciated into  ions,  and  that  these  smaller  particles  conduct  the  electric 
currentandaretheactive  elements  in  most  chemical  reactions.  When 
a  simple  salt  dissolves  in  water,  such  as  sodium  chloride,two  ions 
are  formed,  Na  and  Cl ;  in  this  case  the  ions  coincide  in  chemical 
formula  with  the  atoms,but  they  differ  chemically.  If  we  place  the 
metal  sodium,  with  which  we  are  familiar,  in  water,  an  immediate 
reaction  results  with  the  evolution  of  hydrogen  and  the  formation 
of  caustic  soda;  and  also  the  familiar  chlorine  is  a  gas  of  disagree- 
able odor  and  active  properties,  which  differs  entirely  from  the 
chlorine  ion.  The  difference  between  these  elements  in  the  ordi- 
nary and  in  the  ionic  condition  is  one  of  electric  charge. 

The  ions  do  not  always  coincide  with  the  atoms,  however ;  when 
cupric  sulphate  is  dissolved  in  water  we  have  Cu  and  SO4  ions,  the 
solution  being  blue  on  account  of  the  presence  of  the  Cu  ions ; 
if  a  current  of  electricity  is  passed  through  such  a  solution  the  cop- 
per ions  travel  to  the  cathode;  and  as  the  positive  charges  of  elec- 
tricity they  carry  are  neutralized  by  the  negative  current,  the  blue 
copper  ions  are  converted  to  the  red  metallic  copper  which  de- 
posits on  the  cathode. 

The  electric  charge  carried  by  the  equivalent  weight  in  grams  of 
any  element  or  radicle  is  96,540  coulombs,  so  to  liberate  one  gram 
of  hydrogen  by  the  electrolysis  of  water  we  must  supply  96,540 
coulombs  of  electricity.  As  in  cupric  sulphate,  copper  is  a  diatomic 
element,  the  hydrogen  equivalent  is  one  half  the  atomic  weight,  so 
that  96,540  coulombs  will  deposit  31.8  grams  ;  or  we  may  say  that 
the  cupric  ion  carries  a  double  charge  of  electricity.  This  is 
designated  Cu,  to  show  two  positive  charges.  The  importance  of 
this  quantity  of  electric  charge,  not  only  from  the  theoretical,  but 
also  from  the  practical  standpoint,  is  seen  when  we  consider  solu- 
tions of  an  element  in  two  degrees  of  oxidation  or  where  the  ion 
has  difference  degrees  of  valence  or  of  electric  charge.  Take,  for 
example,  solutions  of  cuprous  and  of  cupric  salts,  with  the  cuprous 
there  is  but  a  single  charge  of  electricity,  with  the  cupric  a  double; 
so  96,540  coulombs  will  deposit  from  a.  cuprous  solution  63.6  grams 
of  copper  and  from  a  cupric  31.8  :  or  if  we  consider  the  amperage, 


IONIZATION.  $ 

the  same  current  will  in  the  same  time  deposit  twice  the  copper 
from  a  cuprous  that  it  will  from  a  cupric  solution. 

This  shows  the  intimate  connection  which  exists  between  the 
valence  of  an  ion  and  its  electric  charge.  It  is  accompanied  often 
by  marked  physical  differences. 

Compare  solutions  of  potassium  manganate  *  and  potassium  per- 
manganate, one  green  the  other  purple,  but  both  composed  of  the 
same  ions,  K  and  MnO4.  The  only  difference  is  that  with  the 
manganate  we  have  K,  K  and  MnO4,  while  with  the  permanganate 
K  and  MnO4,  the  anion  or  negative  ion  has  a  double  charge  in  the 
manganate.  Similarly  there  is  a  difference  between  the  colors  of 
ferrous  chloride  and  of  ferric  chloride  depending  on  whether  the 
Fe  ion  has  two  or  three  positive  charges. 

The  following  list  |  gives  the  most  important  cations  and  anions : 

CATIONS. 

Monwalent.  —  H  in  acids,  K,  Na,  Li,  Cs,  Rb,  Tl,  Ag,  NH4,  Cu 
(cuprous),  Hg  (mercurous). 

Divalent.  —  Ca,  Sr,  Ba,  Mg,  Fe  (ferrous),  Cu  (cupric),  Pb,  Hg 
(mercuric),  Co,  Ni,  Zn,  Cd. 

Irivalent.  —  Al,  Bi,  Sb,  Fe  (ferric). 
Tetravalent.  —  Sn,  Zr. 

ANIONS. 

Monavalent.  —  Qn  in  bases,  F,  Cl,  Br,  I,NO3,  C1O3,  C1O4,  BrO4, 
MnO4  (permanganates)  and  the  anions  of  all  other  monobasic  acids, 
t.  e.t  the  acid  molecule  minus  one  hydrogen  which  goes  to  the 
kathode. 

Divalent.  —  S,  Se,  Te,  SO4,  SeO4,  MnO4  (manganates)  and  the 
anions  of  dibasic  acids. 

Tri-  to  Hexavalent. —  The  anions  of  tri-  to  hexavalent  acids. 
Elementary  anions  with  a  valence  of  more  than  two  are  not  known. 

The  degree  of  ionization  is  measured  most  readily  by  finding 
the  electrical  conductivity  of  the  solution,  for  this  is  dependent  on 
the  number  of  ions  present  and  the  rate  at  which  they  move ;  and 
is  more  convenient  than  obtaining  the  results  from  the  osmotic 
pressure,  on  account  of  the  difficulty  in  making  diaphragms  which 
shall  resist  these  enormous  pressures  and  at  the  same  time  not  let 
through  any  of  the  dissolved  substance.  In  this  way  it  is  shown 
that  most  organic  compounds  are  practically  undissociated  into  ions. 

*  Add  a  little  alkali  to  prevent  rapid  decomposition. 

|  Taken  from  Ostwald's  Scientific  Foundations  of  Analytical  Chemistry. 


4  QUANTITATIVE   ANALYSIS. 

It  is  true  that  organic  acids  and  bases  are  dissociated  in  aqueous 
'solution,  but  the  great  majority  of  the  important  organic  com- 
pounds, such  as  alcohols,  ethers,  carbohydrates,  hydrocarbons,  etc., 
are  practically  without  appreciable  ionization. 

The  extent  of  the  ionization  of  some  of  the  typical  inorganic 
compounds  is  as  follows:  In  a  tenth  normal  solution  most  sim- 
ple salts  such  as  potassium  sulphate,  sodium  nitrate,  potassium 
chloride,  ammonium  chloride  and  so  on,  are  almost  completely  dis- 
sociated. There  are  but  few  exceptions  to  this  statement ;  one  is 
the  salts  of  cadmium  and  another  those  of  mercury,  the  most  im- 
portant being  mercuric  chloride,  and  the  fact  that  the  nitrate  gives 
many  reactions  which  are  not  obtained  from  the  chloride,  may  be 
explained  by  the  inertness  of  the  chloride,  due  to  lack  of  dissocia- 
tion into  ions.  With  acids  the  dissociation  is  into  hydrogen  ions 
and  negative  ions  consisting  of  the  negative  element  or  radicle  as 
ft,  Cl;  H,N03;  H,  C2H3O2;  rf,  rf,SO4;  H,  H,C2O4,etc.  The  con- 
centration  of  the  hydrogen  ions  measures  the  strength  of  the  acid 
In  a  tenth  normal  solution  the  percentage  of  ionization  is  as  fol- 
lows:  Hydrochloric  acid,  99.5  per  cent.;  nitric  acid,  100  per  cent.; 
sulphuric  acid,  69  per  cent;  acetic  acid,  1.4  per  cent;  carbonic  acid, 
0.174  per  cent.;  sulphydric  acid  (H2S),  0.075  per  cent.;  boric  acid, 
0.013  per  cent.  These  values  give  definite  expression  to  the  ideas 
concerning  the  relative  strength  of  acids  though  they  contradict 
some  of  the  old  views  :  for  instance,  it  has  been  often  stated  that 
sulphuric  acid  is  the  strongest,  because  it  will  displace  other  acids 
from  their  salts,  but  it  is  less  ionized  than  hydrochloric  acid,  and 
the  fact  that  when  evaporated  with  sulphuric  acid,  chlorides  are 
changed  to  sulphates,  is  explained  by  the  easy  volatibility  of  hydro- 
chloric acid  and  is  not  a  proof  that  sulphuric  is  the  stronger  acid. 

Similarly  the  strength  of  a  base  depends  on  the  concentration 
of  the  OH  ions.  At  a  dilution  of  tenth  normal,  potassium  hy- 
droxide is  IOO  per  cent,  dissociated,  sodium  hydroxide,  95.3  per 
cent,  and  ammonium  hydroxide  only  1.6  per  cent.  So  that  nitric 
and  hydrochloric  acids  bear  almost  the  same  relation  to  acetic  acid 
as  the  fixed  caustic  alkalies  do  to  ammonia. 

Ionization  increases  with  dilution  to  a  very  marked  degree  so 
that  at  an  infinite  dilution  all  ionizable  substances  are  completely 
dissociated.  The  effect  of  dilution  is  shown  by  the  following 
values  for  monochloracetic  acid:  N/2,  5.4  per  cent,  dissociated; 
,  10  57  per  cent. ;  N/^2,  20  per  cent. 


I  ON  I Z  ATI  ON.  5 

Temperature  has  but  little  effect  on  the  degree  of  ionization,  but 
a  very  considerable  influence  on  the  rapidity  with  which  the  ions 
travel ;  so  that  rise  in  temperature  increases  the  conductivity  of  the 
solution  as  it  increases  the  rate  of  migration  of  the  ions,  and  there- 
fore must  be  considered  in  calculating  the  ionization  from  the  con- 
ductivity. 

So  far  water  alone  has  been  considered  as  the  solvent,  as  it  has 
the  greatest  dissociating  power ;  in  other  solutions  the  degree  of 
ionization  is  much  less;  but  water  itself,  although  usually  con- 
sidered a  non-conductor,  is  dissociated  very  slightly,  and  is  found  to 
contain  one  gram  of  hydrogen  ions  to  twelve  million  liters.  As 
will  be  explained  later  even  this  infinitesimal  ionization  makes 
water  a  reagent  of  importance  in  a  number  of  quantitative  reactions. 

The  reaction  in  neutralizing  sodium  hydroxide  by  hydrochloric 
acid  is  usually  written :  NaOH  +  HC1  =  NaCl  -f  H2O. 

This  represents  the  weights  which  take  part  in  the  reaction  and 
if  we  evaporate  off  the  water,  the  calculated  quantity  of  sodium 
chloride  will  be  obtained.  But  while  in  solution  these  substances 
are  not  all  present  as  molecules,  and  if  we  perform  the  neutral- 
ization with  solutions  more  dilute  than  tenth  normal,  so  that  the 
ionization  of  the  acid,  alkali  and  salt  is  practically  complete,  we 
shall  have : 

Na|OH  +  H|C1  =  Na|Cl  +  H2O 

or  on  both  sides  of  the  equation  we  have  Na  and  Cl  ions,  but  in- 
stead of  H  ions  and  OH  ions  we  have  undissociated  water.  So 
that  the  essential  part  of  this  and  every  other  reaction  of  neutrali- 
zation is  the  formation  of  water.  This  is  strikingly  confirmed  by 
the  fact  that  the  heat  of  neutralization  of  equivalent  quantities  o 
caustic  alkali  by  different  strong  acids  is  the  same,  13,700  calories 
for  the  equivalent  weights  in  grams. 

The  following  may  emphasize  the  importance  of  considering 
what  is  present  in  a  solution  instead  of  what  was  dissolved  to  pro- 
duce it :  Suppose  the  formula  weight  in  milligrams  of  potassium 
chloride  and  the  formula  weight  in  milligrams  of  sodium  nitrate 
are  dissolved  together  in  a  large  volume  of  water  so  that  the  dis- 
sociation is  complete ;  and  that  in  another  vessel  in  an  equally  large 
volume  of  water,  the  formula  weights  in  milligrams  of  potassium 
nitrate  and  of  sodium  chloride  are  dissolved.  The  two  solutions 
are  identical  for  there  are  present  in  each  the  same  number  of  the 
same  four  ions  Na,  K,  Cl  and  NO3. 


6  QUANTITATIVE   ANALYSIS. 

The  characteristic  colors  of  solutions  are  due  either  to  the  color 
of  the  ion  or  the  color  of  the  molecule.  When  solutions  of  nickel 
or  copper  are  evaporated  to  fumes  with  sulphuric  acid,  they  lose 
their  characteristic  colors,  for  when  the  water  has  been  removed 
there  is  no  longer  ionization — or  color.  Cobalt  chloride  dissolved 
in  alcohol  is  blue,  the  color  of  the  molecule  ;  when  water  is  added 
it  becomes  pink,  showing  the  color  of  the  ion.  In  the  same  way 
cupric  chloride  changes  from  brown  to  blue.  The  change  in  the 
colors  of  indicators  is  due  to  the  passing  from  an  ionized  salt  of 
the  indicator  to  an  undissociated  molecule. 

While  it  is  not  claimed  that  there  is  no  reaction  without  ioniza- 
tion it  is  certain  that  in  the  case  of  aqueous  solutions  of  inorganic 
compounds  we  are  dealing  with  ionic  reactions.  In  quantitative 
analysis  most  of  the  tests  are  tests  for  ions,  as  silver  nitrate  for  the 
chlorine  ion;  but  if  sodium  chlorate  is  dissolved  in  water  and  silver 
nitrate  is  added,  no  precipitate  of  silver  chloride  is  produced;  for 
though  there  is  chlorine  present  there  are  no  chlorine  ions,  as  the 
dissociation  is  into  Na  and  C1O3.  Also  with  a  solution  of  sodium 
chlorplatinate  there  is  no  production  of  silver  chloride  but  a  yel- 
low precipitate  of  silver  chlorplatinate  is  formed,  a  test  for  the 
PtCl6  ion. 

When  ammonia  is  added  to  a  solution  of  ferric  chloride  or  any 
other  solution  containing  ferric  ions,  ferric  hydroxide  is  formed ; 
but  no  such  reaction  takes  place  when  it  is  added  to  a  solution  of 
potassium  ferricyanide,  although  it  contains  iron  in  the  ferric  con- 
dition, for  the  ionization  is  into  K  ions  and  Fe  (CN)6  ions.  If  a 
test  for  the  Fe(CN)6  ion  is  applied  in  each  case,  for  example  ferrous 
ions,  nothing  results  with  the  ferric  solution;  while  with  the  ferri- 
cyanide a  characteristic  precipitate  is  formed,  Turnbull's  blue. 

As  inorganic  qualitative  analysis  is  made  up  largely  of  such 
tests  and  separations,  there  is  no  lack  of  further  illustrations  of  the 
application  of  the  theory  of  ionization  to  this  important  branch  of 
analytical  chemistry. 


MASS   ACTION. 


CHAPTER  II. 

Mass  Action. 

In  order  to  understand  the  most  important  effects  of  ionization 
on  quantitative  analysis,  the  law  of  mass  action  must  be  con- 
sidered in  an  elementary  way.  This  will  be  done  by  taking  it  up 
first  in  connection  with  molecular  and  then  with  ionic  dissociation. 

Dissociation  was  the  name  given  originally  by  Deville  to  the 
separation  of  a  molecule  into  smaller  molecules  by  heat.  For  in- 
stance, when  hydriodic  acid  gas  is  heated  above  l8o°C.  it  begins  to 
separate  into  hydrogen  and  iodine.  This  decomposition  increases 
as  the  temperature  is  raised  still  further  and  decreases  on  lowering 
the  temperature  again,  so  that  for  hydriodic  acid  the  amount  of 
dissociation  is  always  the  same  at  a  given  temperature  and  pres- 
sure. This  is  often  expressed  as  follows  :  2HI  ^"^  H2  -f  I2  which 
shows  that  the  reaction  may  go  from  right  to  left  or  from  left  to 
right  depending  on  conditions.  Ammonium  chloride  dissociates 
readily  into  ammonia  and  hydrochloric  acid  gases,  so  that  when 
this  process  is  complete,  there  will  be  present  double  the  number 
of  molecules  and,  according  to  Avogadro's  law,  double  the  pressure 
if  the  volume  is  unchanged.  This  is  a  disturbing  feature  in  those 
methods  of  molecular  weight  determination  which  rely  on  vapor 
density  determinations,  for  the  molecular  weight  decreases  with 
increasing  dissociation  as  the  temperature  rises.  With  sulphur 
the  molecular  weight  at  low  temperatures  shows  eight  atoms  in 
the  molecule,  while  at  86o°C.  there  are  only  S2  molecules  present. 
Ferric  chloride  gives  values  agreeing  with  the  formula  Fe2Cl6  at 
320-440°  but  dissociates  at  higher  temperatures.  Nitric  oxide 
is  a  mixture  of  NO2  and  N2O4,  at  ordinary  temperatures,  but  if  the 
the  temperature  is  raised  the  density  diminishes  until  at  150°  it 
remains  constant  at  22.9  compared  to  H2  as  unity,  which  agrees 
closely  with  the  calculated  weight  for  NO2. 

In  all  such  cases  there  is  for  each  condition  of  temperature  and 
pressure  a  definite  state  of  equilibrium  at  which  the  proportion  of  the 
two  gases  is  constant.  If  "  reaction  velocity  "  is  considered  as  the 
rate  at  which  this  condition  is  approached,  then  the  state  of  equilib- 
rium will  be  that  in  which  the  reaction  velocities  are  equal.  In  the 


8  QUANTITATIVE   ANALYSIS. 


reaction  N2O4  ^I^2NO2.  When  the  state  of  equilibrium  is  reached, 
just  as  much  N3O4  is  formed  in  each  second  by  the  combination  of 
NO,  as  is  dissociated  into  NO2.  While  there  is  reaction  going  on, 
as  the  two  effects  are  equal  in  amount  and  opposite  in  direction, 
the  effect  is  nothing  and  a  condition  of  equilibrium  exists.  The 
principle  that  the  reaction  velocity  at  any  moment  is  proportional 
to  the  masses  of  the  substances  then  present,  is  called  the  law  of 
mass  action. 

Guldberg  and  Waage  found  that  the  rate  of  chemical  action 
(reaction  velocity)  was  proportional  to  the  active  mass  of  each  of 
the  reacting  substances ;  that  is,  to  the  number  of  gram  molecules 
or  formula  weights  per  liter,  whether  as  a  gas  or  in  solution.  The 
following  instances  illustrate  how  important  the  influence  of  mass 
is  in  some  familiar  reversible  reactions :  CaCO,  ^Ttl  CaO  -f  CO2. 
At  high  temperature  we  have  the  condition  of  equilibrium  dis- 
turbed, dissociation  increases  and  if  the  active  mass  of  carbon 
dioxide  is  decreased  by  removing  the  gas  the  tendency  for  the  re- 
verse reaction  is  checked  and  the  reaction  soon  proceeds  com- 
pletely from  left  to  right.  On  the  other  hand,  when  carbon  diox- 
ide is  passed  over  cold  lime  the  reverse  reaction  takes  place. 

When  steam  is  passed  over  red-hot  iron  an  oxide  of  iron  is 
formed  and  hydrogen  ;  while  if  the  oxide  is  heated  in  a  current 
of  hydrogen  aqueous  vapor  and  metallic  iron  are  produced.  The 
action  is  reversible,  depending  on  the  active  mass  of  the  sub- 
stances present ;  in  the  first  case  there  can  be  no  concentration  of 
the  hydrogen  as  it  is  constantly  displaced  by  fresh  quantities  of 
steam  ;  while  in  the  second  case  the  concentration  of  the  steam  is 
prevented  by  the  current  of  hydrogen. 

In  accordance  with  this  law,  if  to  a  dissociated  substance  one  or 
more  of  the  products  of  dissociation  is  added,  the  degree  of  dis- 
sociation is  diminished,  because  the  active  mass  is  increased  and 
the  tendency  to  the  reverse  reaction  strengthened.  When  phos- 
phorus pentachloride  is  vaporized,  it  is  very  largely  dissociated 
into  phosphorus  trichloride  and  chlorine,  but  if  vaporized  in  an 
atmosphere  of  chlorine,  this  is  prevented  by  the  mass  action  of 
the  chlorine  and  the  molecular  weight  is  found  to  correspond  very 
nearly  to  that  calculated  for  phosphorus  pentachloride,  instead  of 
to  about  half  that  value. 

These  principles  have  a  most  important  bearing  on  analytical 
chemistry  :  for  instance,  lead  can  be  precipitated  as  sulphide,  from 


MASS   ACTION.  9 

a  solution  very  slightly  acid  with  hydrochloric  acid ;  while  on  the 
other  hand  lead  sulphide,  whether  natural  or  artificial,  can  be  dis- 
solved readily  in  strong  hydrochloric  acid.  This  is  evidently  a  re- 
versible reaction. 

PbS  +  2HC1  ^t  H2S  +  PbCl2. 


In  order  to  have  it  proceed  from  left  to  right,  the  active  mass  of 
the  hydrochloric  acid  must  be  large  and  that  of  the  sulphuretted 
hydrogen  small.  This  is  accomplished  by  using  a  considerable 
quantity  of  strong  acid  and  allowing  the  sulphuretted  hydrogen  to 
escape  from  an  open  vessel,  or  better  by  heating.  To  get  the  re- 
verse reaction  the  concentration  of  the  acid  must  be  reduced  by 
neutralization  or  dilution,  and  that  of  the  sulphuretted  hydrogen 
increased  by  passing  a  steady  stream  of  the  gas  through  the  solu- 
tion. If  the  lead  is  to  be  precipitated  completely  the  conditions 
must  be  such  that  the  direct  reaction  is  entirely  prevented,  i.  e., 
there  must  be  very  little  acid  present.  The  same  considerations 
apply  to  other  sulphides,  such  as  that  of  cadmium,  and  to  other 
precipitates  as  well. 

EFFECTS  OF  MASS  ACTION  ON  IONIZATION. 

Just  as  the  laws  of  gases  have  been  found  to  apply  to  ions  in 
solution  as  well  as  to  gaseous  molecules,  as  is  shown  by  the  os- 
motic pressures  of  electrolytes,  so  the  law  of  mass  action  is  found 
to  apply  to  the  ions  in  solution  ;  and  the  effect  of  mass  is  the  same, 
whether  the  dissociation  is  like  that  of  gases  into  smaller  molecules 
or  in  solution  of  an  electrolytic  nature  into  ions. 

The  addition  of  an  ion  in  common  drives  back  the  dissociation. 
An  illustration  of  this  is  found  in  the  fact  that  while  aluminum 
hydroxide  is  perceptibly  soluble  in  an  excess  of  ammonia,  this 
solubility  is  diminished  by  the  presence  of  ammonium  chloride  or 
other  ammonium  salt.  As  ammonium  hydroxide  is  slightly  dis- 
sociated and  ammonium  chloride  almost  completely,  the  mass  ac- 
tion of  the  increased  ammonium  ions  drives  back  the  dissociation 
of  the  ammonia,  and  so  readily  diminishes  the  concentration  of  the 
hydroxyl  ions  to  such  an  extent  that  it  is  too  weak  an  alkali  to 
dissolve  aluminum  hydroxide. 

The  weakening  of  acetic  acid  by  the  addition  of  an  acetate,  or 
the  driving  back  of  the  dissociation  by  the  addition  of  an  ion  in 
common,  can  be  very  strikingly  shown  by  the  following  experi- 


io  QUANTITATIVE   ANALYSIS. 

ment:  If  to  a  solution  of  ferric  acetate,  slightly  acid  with  acetic 
acid,  sulphuretted  hydrogen  water  is  added,  no  black  precipitate  is 
found,  but  only  a  separation  of  sulphur  due  to  the  reduction  of  the 
iron ;  but  if  to  another  portion  of  the  same  solution  a  considerable 
quantity  of  sodium  acetate  is  added  and  then  sulphuretted  hydro- 
gen water  as  before,  a  heavy  black  precipitate  of  ferrous  sulphide 
will  form  immediately,  because  the  mass  action  of  the  acetions 
(C2H3O2)  has  driven  back  the  dissociation  of  the  acetic  acid  to  such 
an  extent  that  it  can  no  longer  dissolve  iron  sulphide.* 

To  illustrate  this  action  numerically  let : 

a  =  the  concentration  of  H  ions  in  gram  molecules  per  liter. 

b  =  the  concentration  of  C2H3O2  ions  in  gram  molecules  per  liter. 

r=the  concentration  of  undissociated  acetic  acid  molecules  in 
gram  molecules  per  liter. 

k  =  a  constant. 

The  law  of  mass  action  states  that  the  product  of  the  concentra- 
tions of  the  ionized  portion  equals  that  of  the  undissociated  portion 
times  a  constant,  which  is  dependent  on  the  nature  of  the  substance, 
the  temperature  and  the  pressure ;  or  using  the  letters  to  designate 
these  concentrations  ab  =  kc.  With  acetic  acid  this  would  mean 
that  the  product  of  the  concentrations  of  the  hydrogen  ions  and 
the  acetions  equalled  the  concentration  of  the  molecules  of  acetic 
acid  times  k. 

Let  us  suppose  that  there  are  present  a  weight  of  acetic  acid 
equal  to  that  of  two  hundred  gram  molecules  at  a  dilution  nearly 
tenth  normal,  that  is  very  nearly  6  grams  of  actual  acetic  acid  per 
liter.  We  shall  have  dissociation  to  the  extent  of  about  1 .5  per  cent, 
or  three  gram  hydrogen  ions,  three  gram  acetions  and  one  hundred 
and  ninety-seven  gram  molecules  of  acetic  acid.  Substituting  these 
values  for  a,  b  and  <?,  we  get 

3x3  =  0.04568  x  197. 

Now  if  two  hundred  gram  molecules  of  sodium  acetate  are  added, 
as  this  is  practically  completely  dissociated  into  Na  and  C2H3O2 
ions,  we  are  adding  two  hundred  more  gram  acetions  and  the  situ- 
ation would  be  represented  as  follows  : 

3  x  (200  +  3)  =  0.04568  x  197. 

*For  experiments  illustrating  ionization  mass  action,  etc.,  see  an  article  by  A.  A. 
Noyes  and  Blanchard,  Journal  of  the  American  Chemical  Society,  22,  727,  from  which 
some  of  the  experiments  described  here  are  taken. 


MASS   ACTION.  n 

This  is  evidently  impossible,  and  contrary  to  the  law  of  mass 
action.  The  addition  of  the  acetions  has  disturbed  the  condition 
of  equilibrium  and  it  will  only  be  regained  by  acetions  recombining 
with  hydrogen  ions  and  forming  more  undissociated  molecules  of 
acetic  acid  until  we  again  have  ab  =  kc.  This  occurs  when  ap- 
proximately 2.955  of  the  three  gram  ions  present  have  recombined, 
leaving  0.045  gram  hydrogen  ions,  200.045  gram  acetions  and  form- 
ing 199955  gram  molecules  of  acetic  acid,  giving  0.045  X  200.045 
=  0.04568  x  199  955  or  9  -f  =  9  -f  approximately. 

By  this  means  the  hydrogen  ions  have  been  diminished  from 
three  grams  to  0.045  gram  and  the  percentage  of  dissociation 
reduced  from  1.5  to  0.0225.  So  that  by  the  addition  of  an  equal 
number  of  molecules  of  sodium  acetate  the  acetic  acid  has  been 
made  weaker  than  sulphydric — as  shown  in  the  experiment  with 
ferric  acetate. 

When  the  addition  of  a  completely  ionized  salt  is  made  to  a  sub- 
stance which  is  very  largely  ionized,  like  sodium  chloride  to  hydro- 
chloric acid,  the  effect  is  small.  If  we  consider  in  the  same  way, 
one  hundred  gram  molecules  of  hydrochloric  acid,  ninety  per  cent, 
ionized  we  have, 

(H)9o  x  (Cl)9o  =  810  x  io(HCl) 

a  x  b  =  k  x  c. 

When  one  hundred  gram  molecules  of  sodium  chloride  are  added 
the  immediate  effect  would  be, 

(H)90  x  (0)190  =  810  x  10  HC1, 

and  to  restore  equilibrium  about  eight  more  gram  molecules  of 
hydrochloric  acid  are  formed :  then, 

(H)82  x  (Cl)i82  =  8iox  18. 

So  the  grams  of  hydrogen  ions  are  only  reduced  from  ninety  to 
eighty- two. 

If  the  dilution  were  greater  so  that  the  ionization  would  be  com- 
plete, the  addition  of  a  solution  containing  an  ion  in  common  would 
be  without  effect. 

MASS  ACTION  ON  INDICATORS. 

The  very  confusing  action  of  indicators  is  explained  by  the  mass 
action  of  ions  in  solution.  Only  the  two  indicators  most  gener- 
ally used  will  be  discussed.  Phenol  phthalein  is  an  extremely  weak 
acid,  hardly  dissociated  at  all  in  aqueous  solution,  the  molecule  is 


r 

12  QUANTITATIVE   ANALYSIS. 

colorless,  the  anion  is  red.  If  to  water  containing  a  few  drops  of  a 
very  dilute  solution  of  the  indicator,  a  strong  base  like  sodium 
hydroxide  is  added,  the  sodium  salt  of  the  weak  acid  is  formed, 
which  is  immediately  dissociated  and  an  intense  red  color  is  pro- 
duced, due  to  the  ions.  When  an  acid,  stronger  than  that  of  the 
indicator  is  added  to  the  red  alkaline  solution,  the  first  reaction  is 
with  the  excess  of  alkali,  giving  as  the  net  result  undissociated 
water,  as  already  explained ;  then  the  sodium  salt  of  the  indicator 
is  affected,  yielding  the  nearly  undissociated  phenol  phthalein  ;  and 
if  the  acid  used  is  strong,  the  change  to  colorless  is  instantaneous, 
due  to  the  driving  back  of  the  few  dissociated  molecules  of  the 
phenol  phthalein  by  the  hydrogen  ions  of  the  acid.  To  get  a  sharp 
change  to  colorless  the  concentration  of  the  hydrogen  ions  from 
the  acid  must  be  sufficient  to  drive  back  the  dissociation  of  the 
indicator  by  an  excedingly  small  excess  of  acid.  Hence  the  weaker 
the  acid  of  the  indicator  the  less  the  excess  of  acid  required  to 
turn  it  and  so  phenol  phthalein,  which  is  one  of  the  weakest  acids 
known,  serves  as  an  accurate  indicator  for  the  weak  organic  acid 
as  well  as  for  the  more  highly  ionized  mineral  acids. 

In  passing  from  the  acid  to  the  alkaline  solution  (red  with  phenol 
phthalein)  to  get  a  sharp  change  in  color,  it  is  necessary  that  the 
salt  formed  be  unaffected  by  the  hydrolytic  action  of  the  water 
present.  It  has  been  stated  that  water  was  ionized  though  to  an 
almost  infinitely  small  extent,  but  even  this  has  its  effect,  and  when 
the  salt  formed  is  very  unstable,  as  the  ammonium  salt  of  phenol 
phthalein,  there  is  a  tendency  for  a  reverse  reaction,  NHJR  +  H|OH 
=  NHJOH  -f  HR,*  with  the  formation  of  undissociated  phenol 
phthalein  and  no  color.  This  action  is  entirely  overcome  by  more 
ammonia,  but  it  prevents  a  sharp  end  point  with  this  indicator, 
when  a  weak  base  is  used  for  neutralizing. 

Methyl  orange  is  also  an  acid  but  much  stronger  than  phenol 
phthalein,  the  color  of  the  molecule  is  red,  that  of  the  negative  ion 
yellow.  Like  other  weak  organic  acids,  when  this  indicator  is  dis- 
solved in  water  it  is  partly  dissociated,  so  that  there  are  present 
both  the  red  molecules  and  the  yellow  ions,  which  give  the  so- 
called  neutral  color  of  the  indicator.  The  addition  of  hydrogen 
ions  immediately  drives  back  this  dissociation  and  gives  only  the 
red  molecules  of  the  indicator  (acid  color) ;  while  with  alkali  the 

*  The  phenol  phthalein  radicle  is  designated  by  R. 


MASS   ACTION.  13 

salt  is  formed  which  is  dissociated,  giving  yellow  ions  (alkaline 
color). 

Let  us  now  compare  the  action  of  these  two  indicators.  If  to 
water  containing  each  we  add  an  exceedingly  small  amount  of  an 
acid  which  is  stronger,  more  ionized  than  either,  the  color  of  the 
molecule  is  obtained  with  each.  If  we  add  to  each  an  acid  less 
ionized  than  methyl  orange  but  more  ionized  than  phenol  phthalein, 
this  will  be  without  effect  on  the  methyl  orange,  but  will  drive 
back  the  dissociation  of  the  phenol  phthalein  and  render  it  colorless. 
So  there  are  certain  acids  which  act  differently  with  different  indi- 
cators and  neutrality  must  be  defined  by  reference  to  the  partic- 
ular indicator  employed.  For  example,  carbonic,  sulphurous,  sul- 
phydric  and  boric  acids  do  not  affect  methyl  orange,  but  react  acid 
with  phenol  phthalein. 

As  methyl  orange  is  a  stronger  acid  than  phenol  phthalein,  it 
gives  more  stable  salts.  These  are  less  easily  hydrolysed,  hence 
this  is  a  better  indicator  for  weak  alkalies,  like  ammonia,  than 
phenol  phthalein. 

Phosphoric  acid  affords  one  of  the  best  illustrations  of  the  action 
of  these  indicators ;  it  is  a  tribasic  acid  which  ionizes  strongly  into 
H  and  H2PO4  ions;  then  the  ion  H2PO4  breaks  up  to  a  much 
smaller  extent  into  H  and  HPO4  ions,  while  the  last  dissociation  of 
HPO4  into  H  and  PO4  ions  is  too  small  to  be  shown  accurately  by 
any  known  indicator.  Or,  to  express  this  differently,  the  first  hy- 
drogen acts  like  a  strong  acid,  the  second  like  a  weak  one,  and  the 
third  scarcely  possesses  acid  properties.  If  to  a  solution  of  phos- 
phoric acid  methyl  orange  is  added  and  then  alkali  is  run  in,  the 
change  to  yellow  occurs  when  the  first  hydrogen  has  been  neutral- 
ized, for  the  second  is  a  weaker  acid  than  the  indicator  and  so  does 
not  affect  it.  When  phenol  phthalein  is  used  the  change  in  color 
does  not  take  place  till  the  second  hydrogen  is  replaced,  as  this  is 
sufficiently  strong  to  drive  back  the  ionization  of  this  sparingly 
dissociated  indicator.  One  indicator  marks  the  change  to  NaH2PO4, 
the  other  to  Na2HPO4.  So  that  the  ordinary  phosphate  of  soda, 
although  by  constitution  an  acid  salt,  gives  a  strong  alkaline  re- 
action with  methyl  orange. 

SOLUBILITY  PRODUCT. 

The  last  application  of  the  law  of  mass  action  to  ions  in  solution 
is  the  case  of  a  saturated  solution.  When  silver  is  precipitated  as 


14  QUANTITATIVE   ANALYSIS. 

chloride  in  an  aqueous  solution,  although  silver  chloride  is  one  of 
the  most  insoluble  precipitates,  there  is  still  some  remaining  in 
solution  ;  and  of  this  silver  chloride  in  solution,  a  large  percentage 
is  dissociated,  so  we  have  again  for  the  dissolved  portion,  the 
formula  ab  —  kc.  Here  for  each  precipitate,  kc  is  a  constant  at 
a  given  temperature,  its  size  depending  on  the  solubility  of  the 
precipitate.  This  value  was  termed  by  Nernst  the  solubility  prod- 
uct, and  here,  as  in  the  case  of  an  unsaturated  solution,  we  have  a 
state  of  equilibrium  only  when  ab  =  kc.  If  ab  is  less  than  kc 
some  of  the  precipitate  dissolves.  If  ab  is  greater  than  kc  more 
separates  out.  In  other  words  as  kc  is  a  constant,  the  equilibrium 
is  adjusted  by  increase  or  decrease  of  the  precipitate,  instead  of  by 
a  change  in  the  number  of  undissociated  molecules  in  solution. 
Or,  the  molecules  may  be  regarded  as  first  forming  in  solution 
when  an  ion  in  common  is  added ;  and  then,  as  it  is  in  contact  with 
the  precipitate,  it  can  not  remain  supersaturated  and  so  more  pre- 
cipitate separates  out. 

So,  if  to  a  solution  containing  a  precipitate  of  silver  chloride,  an 
excess  of  silver  nitrate  is  added,  the  concentration  of  the  silver 
ions  is  increased,  the  solubility  product  is  exceeded,  and  silver 
chloride  separates  out  until  ab  again  equals  kc.  In  this  way  the 
addition  of  ten  times  the  silver  ions  present  reduces  the  chlorine 
ions  to  about  one  tenth. 

This  is  the  explanation  of  Mulder's  end  point  in  the  Gay-Lussac 
titration  method,  where  a  portion  of  the  clear  supernatant  liquid 
is  withdrawn  and  to  one  half  silver  nitrate  is  added,  to  the  other 
sodium  chloride ;  when  the  opalescence  in  each  is  equal  the  end 
point  is  obtained. 

This  cloudiness  obtained  with  silver  chloride  must  be  very 
slight  on  account  of  the  insolubility  of  silver  chloride.  The  effect 
of  adding  an  ion  in  common  is  very  strikingly  shown  with  silver 
acetate  which  is  much  more  soluble.  Place  one  hundred  cubic 
centimeters  of  a  saturated  solution  of  silver  acetate  in  each  of  three 
cylinders ;  to  the  first  add  ten  cubic  centimeters  of  ^N  silver 
nitrate,  to  the  second  ten  cubic  centimeters  of  ^N  sodium  acetate, 
to  the  third  several  grams  of  solid  sodium,  nitrate.  With  the  first 
and  second  a  beautiful  crystalline  precipitate  appears,  due  to  the 
exceeding  of  the  solubility  product  by  the  addition  of  either  silver 
or  acetions ;  while  with  the  third  no  precipitate  is  formed,  which 
shows  that  the  addition  of  ions  not  common  to  the  precipitate  is 
without  effect. 


MASS   ACTION.  15 

It  is  evident  that  the  more  soluble  the  precipitate,  the  larger  will 
be  the  solubility  product;  consequently,  the  greater  must  be  the 
excess  of  reagent  added  in  order  to  obtain  equally  complete  pre- 
cipitation. This  has  been  done  by  chemists  for  many  years  as  the 
result  of  careful  quantitative  experiment,  but  the  theory  of  ioniza- 
tion  and  Nernst's  solubility  product  afford  a  satisfactory  explana- 
tion and  show  why  in  precipitates  like  zinc  ammonium  phosphate, 
a  much  greater  excess  of  reagent  is  required  than  with  others  like 
barium  sulphate.  Another  application  of  the  principle  of  driving 
back  the  ionization  or  practically  decreasing  the  solubility  by  the 
addition  of  an  ion  in  common  with  the  precipitate,  is  in  the  wash- 
ing of  precipitates.  Lead  sulphate  is  washed  with  one  per  cent, 
sulphuric  acid,  as  it  was  found  that  it  was  less  soluble  in  this  than 
in  pure  water,  now  the  reason  is  found  in  the  influence  of  the  SO4 
ions.  There  are  many  other  instances,  washing  cadmium  ammo- 
nium and  other  phosphates  with  water  containing  ammonium  phos- 
phate, calcium  oxalate  with  very  dilute  ammonium  oxalate,  etc. 
The  last  of  the  washing  solution  is  removed  by  a  final  washing 
with  dilute  alcohol  in  those  cases  where  it  can  not  be  volatilized. 

COMPLEX  IONS. 

After  having  given  some  of  the  important  applications  of  ioniza- 
tion and  mass  action  to  analytical  work  it  is  necessary  to  give  an 
explanation  for  the  apparent  exceptions  to  the  laws. 

If  to  a  precipitate  of  silver  cyanide  an  excess  of  potassium  cyan- 
ide is  added,  or  if  it  is  washed  with  a  dilute  cyanide  solution,  instead 
of  obtaining  more  complete  precipitation,  the  precipitate  dissolves. 
This  is  due  to  the  formation  of  a  compound,  KAg(CN),,  which 
dissociates  into  K  and  Ag(CN)2  ions.  A  different  ion  is  formed 
which  gives  a  different  set  of  reactions  and  we  could  no  more  ex- 
pect the  Ag(CN)2  ion  to  give  the  reactions  of  the  CN  ion  than  the 
PtG6  ion  to  give  those  of  Cl  or  the  Fe(CN)6  ion  those  of  Fe. 

So  the  apparently  abnormal  results  are  caused  by  a  change  in 
the  ionization. 

During  the  rest  of  this  article  reference  will  be  made  to  these 
modern  theories  only  in  connection  with  quantitative  precipitations, 
so  for  further  information  the  reader  must  consult  the  numerous 
books  on  physical  chemistry  among  which  the  following  are  recom- 
mended :  Ostwald's  Scientific  Foundations  of  Analytical  Chemis- 
try, Walker's  Introduction  to  Physical  Chemistry,  Morgan's  Ele- 
ments of  Physical  Chemistry. 


1 6  QUANTITATIVE   ANALYSIS. 


CHAPTER  III. 

The  Analysis  of  Magnesium  Sulphate  and  the  Determination 
of  Alumina  in  Alum. 

CRYSTALLIZED  MAGNESIUM  SULPHATE. 

When  the  sample  is  first  received  it  should  be  examined  to  find 
out  whether  the  crystals  have  effloresced.  If  they  appear  uniform 
and  show  no  white  at  the  edges,  the  sample  is  probably  homogen- 
eous and  contains  the  full  seven  molecules  of  water  of  crystalliza- 
tion. If  there  is  any  evidence  of  loss  of  water  the  entire  sample 
should  be  thoroughly  mixed  and  about  five  grams  ground  up  in 
an  agate  or  porcelain  mortar  as  quickly  as  possible  and  immedi- 
ately transferred  to  a  small  specimen  tube  which  is  kept  tightly 
stoppered.  When  a  portion  is  desired  for  analysis,  weigh  the 
specimen  tube  containing  the  average  sample;  then  shake  out 
about  a  gram  into  a  beaker,  taking  care  that  all  of  the  powder  re- 
moved gets  into  the  beaker,  stopper  and  reweigh  the  tube.  The 
difference  between  the  weights  gives  the  amount  taken  for  analy- 
sis. This  is  termed  weighing  by  difference. 

DETERMINATION  OF  WATER. 

Heat  a  perfectly  clean  porcelain  crucible  and  cover  over  a  Bun- 
sen  burner  until  all  the  moisture  is  expelled,  allow  it  to  cool  par- 
tially and  then  place  it  in  a  desiccator ;  cover  tightly  and  allow  the 
cooling  to  continue  in  this  dry  atmosphere  till  the  temperature  of 
the  balance  room  is  reached.  Then  weigh  the  crucible  with  its 
cover  and  record  the  weight  in  a  note-book  at  once.  Next  shake 
about  a  gram  of  the  salt  from  the  specimen  tube  into  the  crucible 
and  reweigh  the  tube.  Then  weigh  the  crucible  with  the  salt  to 
see  whether  the  weight  checks  the  sum  of  the  weights  of  the  cru- 
cible and  the  sample  taken.  There  may  be  a  slight  loss  of  water 
during  the  operation  so  that  the  check  is  satisfactory  when  the 
second  weight  is  either  the  same  as  the  sum  of  the  two  or  less  by 
two  or  three  tenths  of  a  milligram.  Place  the  crucible  on  a  pipe- 
stern  triangle  with  the  cover  on  and  heat  it  for  half  an  hour  with 
about  a  four-inch  flame  from  a  Bunsen  burner,  then  allow  to  cool 
partly,  place  in  a  desiccator  and  when  cold  weigh  quickly.  Heat 


MAGNESIUM    SULPHATE.  17 

again  for  ten  minutes  at  the  same  temperature,  cool  and  reweigh. 
If  all  the  water  of  crystallization  has  been  driven  off  by  the  first 
heating  the  two  weights  will  be  identical.  If  they  differ  by  more 
than  two  tenths  of  a  milligram,  the  heating  must  be  continued  till 
a  constant  weight  is  obtained.  Should  the  weight  continue  to  de- 
crease, even  after  heating  for  an  hour,  loss  of  sulphuric  anhydride, 
SO3,  is  indicated  and  the  determination  must  be  repeated  at  a 
lower  temperature.  The  ignition  should  be  made  at  a  moderate 
red  heat,  between  dull  and  bright  red.  With  a  blast  lamp  all  of 
the  sulphuric  anhydride  can  be  driven  off.  A  porcelain  crucible 
is  recommended  for  this  determination  as  it  is  less  likely  to  be 
overheated  than  platinum,  because  it  is  a  much  poorer  conductor. 
A  comparison  of  magnesium  sulphate  with  the  other  alkaline  earth 
sulphates  shows  a  regular  increase  of  stability  with  the  increase  of 
the  atomic  weight  of  the  metal. 

If  the  contents  of  the  crucible  were  allowed  to  stand  in  the  air 
moisture  would  be  reabsorbed  with  an  increase  in  weight. 

From  the  loss  in  weight  the  percentage  of  water  is  calculated. 

DETERMINATION  OF  SULPHURIC  ANHYDRIDE. 

Weigh  out,  by  difference,  into  a  number  two  beaker  about  one 
gram  of  the  salt  (the  exact  weight  being  recorded),  add  about  150 
c.c.  of  hot  water  and  2-3  c.c.  of  dilute  hydrochloric  acid,  cover  with 
a  watch  glass  and  heat  to  boiling ;  while  boiling  add  drop  by  drop 
(so  as  not  to  cool  the  solution)  from  a  pipette  20-25  c-c-  °f  a  ten 
per  cent,  solution  of  barium  chloride,  or  else  dilute  20-25  c.c.  of 
barium  chloride  solution  with  water  to  about  50  c.c.,  heat  to  boil- 
ing and  then  add  it  to  the  boiling  solution  of  magnesium  sulphate. 
Boil  for  at  least  five  minutes,  while  stirring  with  a  thin  glass  rod  to 
avoid  bumping,  then  allow  to  settle.  If  the  precipitate  does  not 
settle  quickly  and  completely,  boil  again  for  several  minutes  or  heat 
just  below  boiling  for  a  longer  time.  Pour  the  clear  supernatant 
liquid  through  a  nine-centimeter  "  ashless  "  filter,  which  has  been 
moistened  with  hot  water,  allowing  the  precipitate  to  remain  as  far 
as  possible  in  the  beaker.  Test  a  few  drops  of  the  filtrate  in  a 
watch  glass  or  small  test-tube  with  dilute  sulphuric  acid  to  make 
sure  that  an  excess  of  barium  chloride  is  present.  Add  100  c.c.  of 
hot  water  and  one  c.c.  of  dilute  hydrochloric  acid  to  the  precipitate 
in  the  beaker ;  stir  well  and  then  allow  the  precipitate  to  settle  ; 
pour  the  liquid  through  the  filter  and  wash  the  precipitate  twice 


1 8  QUANTITATIVE   ANALYSIS. 

more  by  decantation  with  hot  water  alone.  Transfer  the  precipitate 
to  the  filter  with  hot  water  from  a  wash  bottle,  using  a  rubber- tipped 
glass  rod  to  detach  any  particles  which  adhere  to  the  beaker,  and 
continue  the  washing  with  hot  water  on  the  paper  till  the  washings 
show  no  test  for  chlorides,  when  at  least  three  cubic  centimeters  are 
tested  with  silver  nitrate  solution,  or  until  three  cubic  centimeters 
leave  no  residue  when  evaporated  in  platinum. 

If  convenient,  dry  the  precipitate  in  an  air-bath  at  about  1 15°  C.; 
but  this  is  not  necessary  for  this  particular  precipitate.  Place  the 
filter  containing  the  precipitate,  either  moist  or  dry,  in  a  clean, 
weighed  platinum  crucible ;  put  this  on  its  side  on  a  platinum  tri- 
angle with  the  cover  in  front,  so  that  a  current  of  air  shall  pass  in 
and  over  the  filter.  Then  heat  the  cover  by  a  Bunsen  burner  so 
that  heat  shall  be  reflected  into  the  crucible  and  the  precipitate  dried 
from  the  top  down.  When  the  water  is  all  expelled,  heat  the  crucible 
itself  gently  so  as  to  drive  out  the  volatile  matter  from  the  paper 
without  allowing  it  to  take  fire.  When  this  is  expelled  move  the 
flame  to  directly  under  the  bottom  of  the  crucible  and  heat,  using 
a  large  flame,  until  all  the  carbon  is  oxidized.  Allow  the  crucible 
to  cool,  and  moisten  the  contents  with  concentrated  nitric  acid  and 
reheat  till  all  the  acid  is  expelled.  This  must  be  done  gradually 
and  cautiously  to  avoid  loss  by  spattering,  and  with  the  crucible 
vertical  and  the  cover  on  tight.  The  object  is  two-fold,  to  oxidize 
any  carbon  which  may  remain  and  to  convert  any  barium  sulphide, 
reduced  by  the  carbon  of  the  paper,  to  sulphate  (this  can  also  be 
done  by  dilute  sulphuric  acid).  Cool  and  weigh,  then  retreat  with 
nitric  or  sulphuric  acid,  expel  the  acid  and  weigh  again.  The 
two  weights  should  check,  if  the  second  exceeds  the  first  by  more 
than  two  tenths  of  a  milligram,  treat  again  until  a  constant  weight 
is  obtained. 

From  the  weight  of  barium  sulphate  calculate  the  percentage  of 
sulphuric  anhydride. 

PROPERTIES  OF  BARIUM  SULPHATE. 

A  white  and  very  insoluble  precipitate  of  definite  composition. 
If  precipitated  in  a  cold  or  very  dilute  solution  it  comes  down  in 
such  a  finely  divided  state  that  it  invariably  runs  through  the 
filter  paper  unless  allowed  to  stand  for  several  hours.  When  pre- 
cipitated in  a  boiling  solution  and  then  heated  the  particles  are 
larger.  The  theory  of  the  increase  in  size  is  as  follows  :  *  The 

*Ostwald,  "  Scientific  Foundations  of  Analytical  Chemistry." 


MAGNESIUM   SULPHATE.  19 

smaller  the  particle  the  greater  is  the  ratio  of  surface  to  volume ; 
hence  the  greater  proportional  contact  with  the  solution.  Now 
every  precipitate  is  soluble  to  a  certain  extent,  and  although  this  is 
very  small  with  barium  sulphate  —  about  one  part  in  four  hundred 
thousand  —  still  it  is  perceptible  even  in  the  cold  and  is  much  in- 
creased by  heating  the  solution.  When  this  is  done  the  smallest 
particles  dissolve  first,  then  the  solution  becomes  supersaturated 
with  respect  to  the  larger  particles  and  deposits  out  barium  sul- 
phate on  them,  so  as  the  boiling  continues  the  larger  particles 
continue  to  grow  at  the  expense  of  the  smaller.  This  same  action 
goes  on,  though  very  much  more  slowly,  when  the  precipitate  is 
allowed  to  stand  in  contact  with  the  solution  in  the  cold.  In  order 
to  obtain  a  successful  filtration,  this  process  must  proceed  till  the 
size  of  the  particles  exceeds  that  of  the  pores  of  the  filter. 

Barium  sulphate  possesses  to  a  marked  degree  the  property  of 
adsorption,  the  carrying  down  of  salts  from  the  solution  or  a  sort 
of  condensation  of  them  on  its  surface  ;  for  this  reason  a  very 
large  excess  of  barium  chloride  is  objectionable,  although  tend- 
ing to  give  more  complete  precipitation.*  The  salts  carried  down 
in  this  way  do  not  have  their  usual  solubility  and  consequently  are 
removed  very  slowly  by  washing ;  so  it  is  always  necessary  to 
test  the  wash-water  for  chlorides  and  prove  their  absence,  and  not 
to  rely  on  the  fact  that  a  certain  volume  of  water  has  passed 
through  which  would  be  more  than  enough  to  dissolve  all  of  the 
salts  present  under  ordinary  conditions.  The  other  salts  likely  to 
be  carried  down  by  barium  sulphate  are  alkali  and  alkaline  earth 
nitrates,  chlorides,  chlorates  and  sulphates. 

The  precipitate  is  practically  insoluble  in  water,  in  dilute  acetic 
acid  and  in  hydrochloric  acid  when  present  to  the  extent  of  one 
cubic  centimeter  of  dilute  acid  in  one  hundred  cubic  centimeters  of 
water,  but  it  is  very  appreciably  soluble  in  stronger  hydrochloric 
acid  and  more  soluble  in  either  nitric  or  sulphuric  acids.  It  is 
also  soluble  to  some  extent  in  hot  acid  solutions  containing  am- 
monium chloride,  ferric  chloride,  etc.,  and  in  solutions  of  ammo- 
nium acetate,  citrates  and  other  organic  salts. 

The  tendency  of  the  precipitate  to  crawl  up  the  sides  of  the 
beaker  can  usually  be  checked  by  adding  a  few  drops  of  hydro- 
chloric acid  and  boiling.  On  ignition  barium  sulphide  may  be 

*  See  solubility  product  in  Chapter  II. 


20  QUANTITATIVE   ANALYSIS. 

formed  which  can  be  reconverted  to  barium  sulphate  according 
to  the  reactions : 

BaS  +  H2SO4  =  BaSO4  +  H2S  or 
3BaS  +  8HNO3  =  3BaSO4  +  8NO  +  4H2O 

Silica  should  be  absent,  for  if  not  removed  it  may  contaminate  the 
barium  sulphate.  For  the  precipitation  of  barium  sulphate  in  the 
presence  of  iron  see  Chapter  VII. 

DETERMINATION  OF  MAGNESIA. 

Weigh  out  about  a  gram  of  the  salt  by  difference  into  a  small 
beaker ;  dissolve  it  in  about  fifty  c.c.  of  cold  water,  add  five  or  six 
c.c.  of  dilute  hydrochloric  acid  and  then  make  the  solution  slightly 
alkaline  with  ammonia  ;  if  a  precipitate  of  magnesium  hydroxide 
forms  dissolve  this  in  dilute  hydrochloric  acid  and  again  make 
alkaline  with  ammonia  ;  repeat  this,  if  necessary,  till  the  solution 
is  perfectly  clear  when  alkaline.  Next  add  slowly  drop  by  drop, 
from  a  pipette  about  twenty-five  c.c.  of  a  ten  per  cent,  solution  of 
hydro-di -sodium  or  hydro-di-ammonium  phosphate;  stir  vigor- 
ously, avoid  touching  the  sides  of  the  beaker  with  the  stirring  rod, 
and  allow  to  stand  in  a  cool  place  for  an  hour ;  then  add  a  decided 
excess  of  ammonia,  about  30  c.c.  of  ammonia  water,  specific  gravity 
0.96,  and  allow  to  stand  in  the  cold  for  several  hours  longer  —  over 
night  if  convenient. 

If  the  precipitate  is  perfectly  crystalline  filter  and  test  a  few 
drops  of  the  filtrate  with  "  magnesia  mixture  "  to  make  sure  that 
the  PO4  ions  are  present  in  excess.  It  is  better  to  filter  and  test 
the  filtrate  than  to  withdraw  some  of  the  clear  liquid  with  a  pipette 
or  tube,  as  some  of  the  precipitate  usually  floats.  If  an  excess  of 
the  precipitant  is  present  continue  the  filtration  ;  transfer  all  of  the 
precipitate  to  the  filter  (9  cm.)  and  wash  with  very  dilute  ammonia, 
one  part  of  strong  ammonia  water  to  nine  of  water  (about  2.5  per 
cent,  actual  ammonia)  till  free  from  chlorides,  as  shown  by  no 
cloudiness  being  produced  when  three  c.c.  of  the  washings,  acidi- 
fied with  nitric  acid,  are  tested  with  a  solution  of  silver  nitrate. 
Place  a  large  filter  on  the  top  of  the  funnel  to  keep  out  dust,  put 
it  in  an  air-bath  and  dry  at  from  II5°-I2O°  C.  When  dry  sepa- 
rate the  precipitate  from  the  paper  over  black  glazed  paper  and 
cover  the  precipate  with  a  watch  glass ;  burn  the  paper,  moistened 
with  nitric  acid,  in  a  weighed  platinum  crucible  until  perfectly 


MAGNESIUM   SULPHATE.  21 

white,  adding  more  nitric  acid  if  necessary  ;  then  add  the  portion  of 
the  precipitate  from  the  paper  and  ignite,  at  first  gently  and  then 
strongly,  by  the  full  heat  of  a  burner  or  with  a  blast  lamp  ;  cool 
and  weigh  the  magnesium  pyrophosphate  and  calculate  the  per- 
centage of  magnesia.* 

Magnesium  as  well  as  other  phosphates  attack  platinum  in  the 
presence  of  reducing  agents ;  this  is  another  reason  for  burning  at 
a  low  heat  and  reoxidizing  by  the  addition  of  nitric  acid  before 
heating  strongly.  Phosphides  may  be  formed  even  by  the  reduc- 
ing gases  from  the  flame  penetrating  the  hot  platinum.  If  the 
crucible  is  rough  or  crystalline  after  the  ignition  of  a  phosphate,  it 
should  be  scoured  with  sea  sand,  as  this  crystallization  gradually 
penetrates  and  finally  injures  the  crucible. 

PROPERTIES  OF  MAGNESIUM  AMMONIUM  PHOSPHATE. 

Magnesium  ammonium  phosphate  contains  six  molecules  of 
water  of  crystallization ;  it  is  white  and  distinctly  crystalline;  forms 
slowly  when  present  in  small  quantity ;  its  separation  is  accelerated 
by  cold  and  agitation.  If  at  all  flocculent,  it  is  contaminated, 
most  often  by  magnesium  hydroxide  or  by  hydrated  silica.  The 
magnesium  hydroxide  is  caused  by  insufficient  ammonium  chloride 
being  present  to  so  weaken  the  ionization  of  the  ammonia  that  the 
solubility  product  of  magnesium  hydroxide  shall  no  longer  be  ex- 
ceeded. This  statement  is  based  on  recent  work  f  and  is  accepted 
by  Ostvvald  in  place  of  the  previous  theory  based  on  the  formation 
of  a  complex  ion. 

If  silica  is  present,  it  is  best  to  proceed  as  usual  and  weigh  the 
magnesium  pyrophosphate  plus  silica ;  then  dissolve  out  the  pyro- 
phosphate by  dilute  hydrochloric  acid,  filter  and  ignite  the  silica 
which  is  insoluble,  as  it  has  been  dehydrated  by  the  ignition  of  the 
precipitate,  and  deduct  the  weight  from  that  of  impure  precipitate. 

Magnesium  ammonium  phosphate  is  slightly  soluble  in  cold 
water,  one  part  in  15,000,  but  very  readily  soluble  in  hot  water; 
it  is  insoluble  in  dilute  ammonia  which  has  an  ion  in  common.  If 
the  ammonia  is  very  strong,  the  precipitate  may  be  too  basic, 
contain  more  than  the  right  amount  of  magnesium,  hence  it  is 
precipitated  from  a  solution  which  contains  but  a  slight  excess  of 

*  For  all  calculations,  the  reader  is  referred  to  the  "  Calculations  of  Analytical  Chem 
istry  "  by  E.  H.  Miller,  which  is  used  as  a  text-book  with  these  notes, 
•f"  Loven,  Z.,  Anorganische  Chemie,  II,  404,  1896. 


22  QUANTITATIVE   ANALYSIS. 

ammonia,  to  which,  after  the  precipitate  has  formed,  a  decided 
excess  of  ammonia  is  added  to  render  the  precipitation  more  com- 
plete. In  washing,  very  dilute  ammonia  should  be  used  as  the 
excess  of  hydrodisodic  phosphate,  the  usual  reagent,  is  sparingly 
soluble  in  strong  ammonia.  The  precipitate  is  readily  soluble  in 
acids.  On  ignition,  the  water  of  crystallization  is  driven  off  and 
also  water  and  ammonia  from  the  molecule  giving  pyrophosphate. 

2MgNH4P04.6H20  -f  heat  =  Mg2P2O7  +  2NH3  +  I3H2O. 

It  is  advisable  to  dry  this  particular  precipitate  before  ignition 
as  it  retains  gases  from  the  paper  which  leave  carbon  so  intimately 
mixed  with  the  precipitate  that  it  is  very  difficult  to  burn  out. 
The  pyrophosphate  will  stand  the  heat  of  a  blast  lamp  without 
loss.  If  a  loss  takes  place  some  other  magnesium  ammonium 
phosphate  was  present  and  the  results  are  unreliable. 

This  compound  is  also  used  for  the  determination  of  phosphoric 
acid  and  will  be  mentioned  again  under  iron  ore.  In  the  analysis 
of  crystallized  magnesium  sulphate  the  percentages  of  water, 
sulphuric  anhydride  and  magnesia  should  add  up  to  one  hundred 
per  cent,  whether  the  sample  has  lost  water  or  not.  Ostwald  has 
recommended  calculating  the  results  of  analyses  to  the  ions  present, 
for  example  to  Mg  and  SO4,  instead  of  to  MgO  and  SO3,  but  as 
the  method  given  here  is  in  general  use  and  is  more  convenient 
for  metallurgical  calculations,  the  old  practice  will  be  adhered  to  in 
these  notes. 

For  more  information  on  the  phosphates  of  magnesium  see 
Ncubauer,  Journal  American  Chemical  Society,  Vol.  16,  p.  290. 

POTASSIUM  ALUM. 

Alums  are  double  sulphates  of  the  alkali  metals  and  of  a  triad 
metal  and  contain  twenty-four  molecules  of  water  of  crystallization  ; 
for  example,  K2SO4.A12(SO4)3.24H2O;  Na2SO4.Mn2(SO4)3.24H2O; 
(NH4)2SO4.Cr2(SO4),.24H2O,  etc.  The  formulae  are  often  divided 
and  written  KA1(SO4)2.I2H2O,  etc.  There  are  many  other  double 
sulphates  which  are  not  alums,  for  example  Mohr's  salt,  FeSO4- 

(NH4)2S04.6H20. 

DETERMINATION  OF  ALUMINA. 

Weigh  out  either  by  difference  or  quickly  on  a  watch  glass  about 
one  gram  of  potassium  alum  ;  transfer  it  to  a  number  two  beaker 
and  dissolve  in  about  100  c.c.  of  hot  water  and  five  or  six  c.c.  of 


POTASSIUM   ALUM.  23 

concentrated  hydrochloric  acid  ;  make  slightly  alkaline  with  am- 
monia avoiding  more  than  enough  to  make  the  solution  smell 
faintly  of  ammonia  while  hot.  If  too  much  be  added,  neutralize 
it  by  dilute  hydrochloric  acid.  Heat  to  boiling,  while  stirring  con- 
tinually to  avoid  "  bumping,"  and  allow  the  gelatinous  precipitate 
of  aluminum  hydroxide  to  settle  ;  decant  the  clear  solution  through 
the  filter  and  wash  the  precipitate  four  or  five  times  with  100  c.c. 
of  boiling  water,  stirring  up  thoroughly  each  time  and  decanting 
through  the  filter ;  transfer  to  the  paper  with  hot  water  and  wash 
with  hot  water  till  the  washings  give  no  test  for  chlorides  or 
sulphates. 

This  precipitate  is  extremely  hard  to  wash  on  account  of  its 
gelatinous  nature  and  must  neither  be  allowed  to  stand  before  fil- 
tration, as  it  becomes  insoluble  and  adheres  to  the  beaker,  nor 
should  it  be  allowed  to  stand  over  night  on  the  filter  unless  com- 
pletely washed,  for  it  contracts  on  drying,  leaving  cracks  through 
which  all  the  wash-water  passes,  making  it  impossible  to  remove 
the  salts  by  washing. 

It  is  unnecessary  to  separate  this  precipitate  from  the  paper  and 
no  especial  precautions  are  required  in  igniting ;  as  the  alumina  is 
neither  easily  reduced  nor  volatile  if  the  chlorides  have  been  re- 
moved. Weigh  the  alumina  and  calculate  the  percentage. 

PROPERTIES  OF  ALUMINUM  HYDROXIDE. 

Aluminum  hydroxide  when  freshly  precipitated  is  very  readily 
soluble  in  acids,  both  strong  and  weak,  but  on  standing  it  becomes 
difficultly  soluble  even  in  hydrochloric  acid ;  it  is  also  soluble  in 
caustic  alkalies  and  to  a  slight  extent  in  ammonia.  In  the  plan 
just  given  the  solvent  action  of  the  slight  excess  of  ammonia  is  so 
weakened  by  the  mass-action  of  the  ammonium  ions  from  the  am- 
monium chloride,  that  it  is  no  longer  a  sufficiently  strong  alkali  to 
dissolve  aluminum  hydroxide.  The  action  of  strong  alkali  in  dis- 
solving alumina  is  to  make  this  very  weak  base  take  the  part  of  an 
acid  so  that  the  cation  Al"'  is  changed  to  an  anion  A1O3. 

A  difficulty  which  may  possibly  arise  is  contamination  by  basic 
sulphates  of  aluminum  and  which  may  be  most  readily  avoided  by 
pouring  the  aluminum  solution  into  an  excess  of  ammonia. 

The  precipitate  is  in  general  likely  to  be  contaminated  by  those 
metals  whose  hydroxides  are  precipitated  in  a  weakly  alkaline  so- 
lution such  as  iron,  manganese,  chromium;  also  magnesium,  zinc, 


24  QUANTITATIVE   ANALYSIS. 

cobalt,  nickel  and  copper;  also  phosphates  and  arsenates,  calcium 
carbonate  and  hydrated  silica.  It  is  because  there  are  so  many 
possible  contaminants,  whose  separation  is  difficult,  that  alumina 
is  often  determined  by  difference ;  that  is,  the  total  weight  of  the 
precipitate  is  taken  and  deductions  made  for  the  impurities  from 
the  results  of  separate  determinations. 

Organic  acids,  such  as  tartaric  and  citric,  and  also  sugar  and 
glycerin,  prevent  the  precipitation  of  the  hydroxide.  The  alumina 
obtained  after  strong  ignition  is  insoluble  in  acids,  but  can  be  ob- 
tained as  a  readily  soluble  aluminate  by  fusing  with  alkalies,  either 
caustic  or  carbonate. 

For  the  analysis  of  bauxite  and  of  aluminum  alloys,  see  Handy, 
Journal  American  Chemical  Society,  18,  766,  1896;  Phillips  and 
Hancock,  same,  20,  207,  and  Lunge,  "  Chemisch-technische  Un- 
tersuchungs  Methoden,"  Vol.  II.,  p.  349  and  seq. 


COAL   ANALYSIS.  25 


CHAPTER  IV. 
Coal  Analysis. 

SAMPLING. 

In  all  analytical  work  it  is  of  the  utmost  importance  that  the 
small  portion  taken  for  analysis  accurately  represents  the  average 
composition  of  the  lot  whose  analysis  is  desired ;  otherwise  the 
analysis  is  worthless  and  misleading  for  practical  purposes.  This 
is  especially  true  with  coal,  where  not  only  may  the  sulphur  and 
ash  be  irregularly  distributed,  but  the  amount  of  moisture  may 
vary  from  day  to  day,  depending  on  the  weather ;  if  exposed  to 
rain  or  sunshine  the  percentage  of  water  differs  and  for  this  reason, 
a  carload  may  have  a  different  composition  when  it  arrives  at  its 
destination  from  that  which  it  possessed  when  mined.  These  dis- 
cordant results  should  however  agree,  when  calculated  to  the  dry 
basis  if  the  sampling  has  been  done  correctly. 

The  sample  received  by  the  chemist  should  be  at  least  5  pounds. 
This  is  to  be  crushed  up  immediately,  so  as  to  avoid  any  loss  of 
water  and  quartered,  until  about  a  half  pound  is  obtained ;  this  is 
then  ground  to  4O-mesh  and  divided  in  half,  and  one  half  im- 
mediately sealed  as  a  reserve  sample  in  case  of  dispute  or  accident. 
The  remaining  sample  is  weighed  and  air  dried  at  8o-9O°C.,  al- 
lowed to  cool  in  the  air,  and  the  amount  of  moisture  determined. 
It  is  mixed  up  thoroughly  on  glazed  paper  and  quartered  down  to 
about  twenty  grams  which  are  ground  fine  (loo-mesh)  and  used 
for  the  analysis.  The  object  of  this  treatment  is  to  obtain  the 
water  in  the  sample  as  received  before  it  has  a  chance  to  dry  out 
in  the  warm  atmosphere  of  a  laboratory,  and  to  obtain  an  air-dried 
average  sample,  which  is  not  likely  to  lose  or  absorb  moisture, 
from  which  to  weigh  out  portions  for  analysis.  It  is  to  be  borne 
in  mind  that  water  is  still  present  in  the  coal  and  that  in  calcu- 
lating the  analytical  results  to  the  original  sample  the  loss  in 
weight  in  air  drying  must  be  considered.  This  is  most  readily  ac- 
complished, if  we  regard  the  original  sample  as  made  up  of  a  cer- 
tain weight  of  air-dried  sample  plus  a  certain  weight  of  water  and 
correct  our  percentages  accordingly. 

These  principles  apply  with  equal  or  even  greater  force  to  large 
lots  of  ore,  matte,  slag,  etc. 


26  QUANTITATIVE   ANALYSIS. 

PROXIMATE  ANALYSIS. 

Moisture. — Dry  one  gram  of  the  coal  in  an  air-bath  in  an  open 
porcelain  or  platinum  crucible  for  one  hour  at  a  temperature  be- 
tween 104°— IO7°C.  Cool  in  a  desiccator  and  weigh  covered.  The 
loss  in  weight  is  moisture.  This  apparently  simple  determination 
is  very  difficult  if  extraordinary  accuracy  is  required,  as  water  may 
be  lost  during  the  fine  grinding  of  the  sample,  and  also  because 
all  the  water  may  not  be  given  off  in  an  hour  at  the  temperature 
given.  It  is  however  the  standard  method  and  is  sufficiently  ac- 
curate for  technical  purposes ;  the  error  being  probably  less  than 
that  of  sampling. 

Volatile  Combustible  Matter.  —  Place  one  gram  of  the  air-dried 
sample  in  a  platinum  crucible,  weighing  20-30  grams,  and  having 
a  well-fitting  cover.  Heat  over  the  full  flame  of  a  Bunser  burner 
for  seven  minutes.  The  crucible  should  be  supported  on  a  plati- 
num triangle  with  the  bottom  6-8  cm.  above  the  top  of  the  burner. 
The  flame  should  be  25  cm.  high,  and  the  determination  made  in 
a  place  free  from  draughts.  The  upper  surface  of  the  cover  should 
burn  clean  but  the  under  surface  remain  covered  with  carbon.  To 
find  the  volatile  combustible  matter  subtract  the  percentage  of 
moisture  from  the  percentage  of  loss  found  here. 

This  method  is  evidently  arbitrary  and  open  to  the  objections  of 
the  possibility  of  oxidation  on  one  hand  and  incomplete  expul- 
sion of  the  volatile  matter  on  the  other ;  but  by  following  it  care- 
fully the  results  possess  uniformity,  if  not  scientific  accuracy,  and  it 
is  the  method  in  general  use.  The  loss  due  to  oxidation,  particu- 
larly with  coke,  can  be  diminished  by  using  a  much  larger  sample, 
say  10  grams.  With  coke  the  last  of  the  volatile  matter  should  be 
removed  by  a  couple  of  minutes  over  a  blast  lamp. 

Ash.  —  Burn  the  portion  of  powdered  coal  used  for  the  deter- 
mination of  moisture,  at  first  over  a  very  low  flame,  with  the  cruci- 
ble open  and  inclined,  till  free  from  carbon.  This  sample  can  be 
burned  much  more  quickly  than  the  dense  carbon  or  coke  left  from 
the  determination  of  the  volatile  combustible  matter. 

Fixed  carbon  is  found  by  difference.  Either  subtract  the  per- 
centage of  ash  from  the  percentage  of  coke  (residue  left  when 
water  and  volatile  matter  are  driven  off)  or  subtract  the  sum  of  the 
other  percentages  from  100. 


COAL   ANALYSIS.  27 

DETERMINATION  OF  SULPHUR. 

Sulphur  exists  in  coal  in  three  conditions  —  as  sulphide,  FeS2,  as 
alkaline  earth  sulphate,  CaSO4,  and  as  an  organic  compound.  On 
heating  FeS2,  out  of  contact  with  the  air,  Fe7S8  is  usually  left 
behind.  So  in  the  determination  of  the  volatile  combustible  mat- 
ter, the  sulphur  present  as  an  organic  compound  (if  any)  and  nearly 
one  half  the  sulphur  present  as  pyrites  is  driven  off.  And  in 
burning  off  the  fixed  carbon  the  Fe7S8  is  changed  to  Fe2O3  with 
a  loss  of  the  sulphur  remaining  from  the  pyrites.  The  ash  con- 
tains the  sulphate  sulphur. 

It  was  formerly  customary  to  consider  all  the  sulphur  was  pres- 
ent as  FeS2,  and  that  one  half  of  this  went  off  with  the  volatile 
matter  and  the  second  half  with  the  fixed  carbon;  so  that  one  half 
the  percentage  of  sulphur  was  subtracted  from  each  of  these  per- 
centages to  make  the  results  add  up  to  100  per  cent.  Although 
this  method  is  still  in  use  it  is  evidently  not  strictly  in  accordance 
with  the  facts  and,  as  it  is  never  correct  to  state  more  in  a  report 
than  is  actually  known,  it  is  preferable  to  report  the  percentage 
of  sulphur  separately  and  let  the  sum  of  the  other  determinations 
add  up  to  100  per  cent. 

When  the  sulphur  in  the  ash  is  desired  separately  from  the  total 
sulphur,  a  large  portion,  10-12  grams,  of  the  coal  is  burned  and 
the  sulphur  determined  in  the  ash  by  methods  similar  to  those 
which  will  be  given  under  iron  ore  and  slag  analysis. 

Total  Sulphur.  Eschka  Method  Modified. — One  gram  of  the  finely 
pulverized  coal  is  mixed  with  one  gram  of  light  magnesium  oxide  and 
0.5  gram  of  anhydrous  sodium  carbonate  in  a  platinum  dish  having 
a  capacity  of  75-100  c.c.  or  a  Meissen  porcelain  crucible,  and  heated 
with  an  alcohol  lamp.  When  great  accuracy  is  not  required  a  gas 
burner  may  be  used,  the  dish  being  protected,  as  far  as  possible, 
from  the  products  of  combustion,  which  contain  sulphur.  The 
mixture  is  stirred  frequently  with  a  stout  platinum  wire  or  glass 
rod  and  the  heat  applied  gradually,  especially  with  soft  coals,  until 
strong  glowing  has  ceased ;  then  the  heat  is  increased  until  in  fif- 
teen minutes  the  bottom  of  the  dish  is  at  a  low  red  heat,  which 
is  maintained  until  all  the  carbon  is  burned  out.  The  residue 
which  should  be  nearly  white  and  porous  is  transferred  to  a  No.  2 
beaker  with  about  50  c.c.  of  water,  15  c.c.  of  bromine  water  are 
added  and  the  whole  boiled  for  at  least  5  minutes,  allowed  to  settle 


28  QUANTITATIVE   ANALYSIS. 

and  decanted  through  a  filter  and  boiled  a  second  and  third  time 
with  30  c.c.  of  water  and  then  washed  very  thoroughly  with  hot 
water.  The  filtrate  is  acidified  with  hydrochloric  acid  so  as  to 
have  an  excess  of  about  I  c.c.  and  boiled  to  expel  any  free  bro- 
mine. Then  to  the  hot  solution  barium  chloride  (10  per  cent, 
solution)  is  added  drop  by  drop,  until  10  c.c.  have  been  added  and 
the  solution  boiled  or  heated  on  a  water-bath  until  the  precipitate 
settles  quickly/  filtered  and  treated  as  already  described.  From 
the  weight  of  BaSO^  the  percentage  of  sulphur  is  calculated. 

The  treatment  with  magnesium  oxide,  sodium  carbonate  and 
air,  oxidizes  the  sulphur  present  to  sulphurous  and  sulphuric  anhy- 
drides which  combine  with  the  bases  present.  The  mass  must  not 
fuse  as  it  would  then  be  much  more  difficult  to  oxidize  and  as  the 
silica  from  the  ash  would  thereby  be  rendered  soluble.  It  is  for 
these  reasons  that  magnesia  is  selected  on  account  of  its  bulk  and 
infusibility. 

When  the  mass  is  leached  the  soluble  sulphites  and  sulphates 
pass  into  solution,  together  with  the  excess  of  sodium  carbonate, 
while  the  bulk  of  the  magnesia  and  the  ash  remain  insoluble.  It 
is  at  this  point  that  an  important  reaction  takes  place,  the  ash  may 
contain  calcium  sulphate  which  is  acted  on  by  the  excess  of  sodium 
carbonate,  giving  calcium  carbonate  which  remains  behind  and 
sodium  sulphate  which  passes  into  solution,  and  by  this  means  the 
total  sulphur  is  obtained  in  the  filtrate. 

The  bromine,  in  the  alkaline  solution,  oxidizes  any  sulphites 
present  to  sulphates.  It  is  important  to  acidify  after,  not  before 
filtering,  as  the  latter  would  take  magnesia  into  solution  ;  also  alka- 
line earth  carbonates  which  would  immediately  react,  giving  in- 
soluble sulphates  and  so  cause  low  results. 

The  solution  after  filtration  is  made  but  slightly  acid  and  a 
liberal  excess  of  barium  chloride  is  added  to  get  complete  precipi- 
tation of  all  the  sulphur  as  barium  sulphate. 

This  method  is  most  satisfactory,  but  for  very  accurate  results 
certain  precautions  not  already  mentioned  must  be  observed : 

The  magnesia  and  the  sodium  carbonate  must  be  tested  for  sul- 
phur as  they  often  contain  small  quantities  which  are  enough  to 
interfere  with  the  accuracy  of  the  determination.  If  present  the 
sulphur  should  be  determined  in  2O-gram  lots  and  the  percentage 
marked  on  the  reagent  bottles  and  deducted  from  the  results. 

The  residue  after  leaching  may  in  some  cases  contain  sulphur, 

VOL.  XXV — 4. 


COAL   ANALYSIS.  29 

if  much  calcium  sulphate  should  be  present  and  the  excess  of 
sodium  carbonate  be  insufficient  to  convert  it.  In  such  a  case 
the  residue  is  treated  with  hydrochloric  acid  and  filtered,  the 
filtrate  neutralized  closely  and  any  sulphate  precipitated  as  ba- 
rium sulphate  and  added  to  that  obtained  in  the  main  portion. 

The  original  barium  sulphate  may  be  contaminated  by  silica.  If 
the  heat  has  been  too  high  or  the  ash  very  siliceous,  some  sodium 
silicate  may  be  formed,  dissolved  and  hydrated  silica  be  carried 
down  with  the  barium  sulphate.  To  avoid  this,  evaporate  the  solu- 
tion to  dryness  after  the  bromine  is  boiled  out  and  heat  at  120°  C. 
until  the  hydrochloric  acid  is  driven  off  to  render  the  silica  insolu- 
ble ;  then  take  up  with  hydrochloric  acid  and  water,  filter  and  de- 
termine the  sulphur  as  usual  in  the  filtrate. 

For  further  information  see  Report  to  American  Chemical  Soci- 
ety, Jour.  Amer.  Chem.  Soc.,  21,  1119,  and  Stoddart  on  the  "  Deter- 
nation  of  Sulphur  in  Coal,"  /.  c.y  24,852. 


3o  QUANTITATIVE   ANALYSIS. 

CHAPTER  V. 
Ferric  Ammonium  Alum. 

DETERMINATION  OF  FERRIC  OXIDE  GRAVIMETRICALLY. 

By  Ignition. — As  this  compound  contains  only  ferric  sulphate, 
ammonium  sulphate  and  water,  simple  ignition  will  drive  off  every- 
thing except  ferric  oxide.  So  the  percentage  can  easily  be  found 
by  igniting  a  gram  in  a  weighed  platinum  crucible  to  constant 
weight.  In  order  to  decompose  the  ferric  sulphate  more  readily 
than  by  heat  alone,  a  little  ammonium  carbonate  is  often  added 
and  then  the  residue  reignited.  The  reaction  is  Fe2(SO4)3  -f 
3(NHJ2C03  =  Fe,0,  +  3(NH4)2SO4  +  3CO2. 

The  application  of  this  method  is  extremely  limited,  and  even 
with  this  alum,  if  impurities  were  present  they  would  contaminate 
the  ferric  oxide. 

By  Precipitation  with  Ammonia. — Dissolve  about  a  gram  of  the 
alum  in  hot  water  and  a  few  c.c.  of  hydrochloric  acid,  heat  to  boil- 
ing and  add  at  once,  but  carefully  to  avoid  spattering,  an  excess 
of  ammonia  ;  heat  till  the  precipitate  collects  well ;  decant  through 
a  filter  and  wash  by  decantation  and  then  on  the  filter  with  hot 
water,  till  free  from  chlorides.  Transfer  the  paper  and  precipitate 
to  a  weighed  platinum  crucible  and  moisten  with  strong  nitric 
acid  ;  ignite  gently  till  the  water  and  volatile  matter  have  been  ex- 
pelled; then  allow  to  cool,  moisten  again  with  nitric  acid  and 
burn  out  the  carbon  ;  ignite  and  weigh  ;  check  by  moistening  once 
more  with  nitric  acid  and  reweighing ;  calculate  the  percentage  of 
Fe.O,. 

In  this  particular  analysis,  the  only  difficulty  is  in  avoiding  any 
reduction  of  the  ferric  oxide  by  the  paper,  for  if  once  reduced  to 
the  magnetic  oxide,  reoxidation  is  difficult.  In  general,  however, 
when  iron  is  precipitated  by  ammonia  certain  precautions  must  be 
observed. 

The  iron  must  all  be  in  the  ferric  condition  as  ferrous  iron  is  not 
completely  precipitated  by  ammonia,  but  a  white  precipitate  of 
ferrous  hydroxide  is  formed  which  immediately  turns  green ;  with 
mixtures  of  ferrous  and  ferric  iron,  green,  black  or  brownish  pre- 
cipitates are  formed. 


FERRIC   AMMONIUM   ALUM.  31 

When  the  higher  groups  have  been  previously  removed  by 
sulphuretted  hydrogen,  the  iron  is  conveniently  reoxidized  by  nitric 
acid  or  hydrogen  peroxide. 

In  the  alum  we  did  not  boil  out  the  excess  of  ammonia,  but  if 
there  are  present  elements  of  the  fifth  periodic  group,  phosphorus, 
arsenic,  vanadium,  etc.,  the  excess  of  ammonia  must  be  expelled  in 
order  to  obtain  complete  precipitation  of  the  iron.  Under  these 
conditions  phosphorus,  vanadium,  arsenic  and  antimony  are  carried 
down  as  well,  in  combination  with  the  iron  as  FePO4,  etc. 

Should  we  wish  to  use  the  filtrate  for  the  determination  of  sul- 
phur, we  must  proceed  differently,  as  there  is  danger  that  the 
ferric  hydroxide  may  be  contaminated  by  a  basic  ferric  sulphate ; 
although  this  would  not  cause  any  inaccuracy  in  the  iron  determi- 
nation, as  the  sulphuric  anhydride  would  be  driven  off  on  strong 
ignition.  In  this  case  pour  the  acid  ferric  solution  into  a  large 
beaker  containing  200  c.c.  of  water  and  an  excess  of  ammonia  over 
that  required  to  precipitate  the  iron  and  neutralize  the  acid  pres- 
ent. In  this  way  the  ammonia  will  always  be  in  excess  and  the 
danger  of  forming  basic  sulphates  near  the  neutral  point  is  avoided. 

The  presence  of  ammonium  chloride,  or  other  ammonium  salts, 
favors  the  separation  of  the  hydroxide  and  prevents  its  becoming 
colloidal.  They  must  be  washed  out,  however,  to  prevent  loss  of 
ferric  chloride  on  ignition.  Ferric  hydroxide  is  soluble  in  acids 
both  weak  and  strong,  and  insoluble  in  alkalies.  Its  precipitation 
is  prevented  by  citric  acid,  tartaric  acid  and  other  organic  sub- 
stances such  as  sugar,  glycerine,  etc.,  because  they  form  complex 
ions  containing  Fe,  which  no  longer  give  the  reaction  of  the 
ferric  ion. 

This  precipitate  is  very  likely  to  be  contaminated  not  only  by 
sulphates,  phosphates,  arsenates,  etc.,  as  already  mentioned,  but 
also  by  hydrated  silica  and  by  the  hydroxides  of  aluminum, 
chromium,  manganese,  and  also  by  those  of  magnesium,  cobalt, 
nickel,  zinc  and  copper.  Of  the  latter,  magnesium  and  zinc  can 
be  removed  by  reprecipitation,  but  with  copper,  nickel  and  cobalt 
the  separation  is  not  easy.  As  these  elements,  or  some  of  them, 
are  always  present  in  iron  ores,  the  gravimetric  method  is  seldom 
used  except  to  throw  down  together  hydroxides  of  aluminum  and 
iron  with  phosphoric  acid. 

One  other  property  of  ferric  salts  should  be  mentioned,  the  effect 
of  water  on  them.  Ferric  iron  is  a  very  weak  base  and  when  com- 


32  QUANTITATIVE    ANALYSIS. 

bined  with  a  weak  acid  in  a  neutral  solution  it  is  easily  hydrolysed, 
especially  on  heating,  with  the  formation  of  basic  ferric  salts.  It 
is  for  this  reason  that  hydrochloric  acid  is  added  to  the  alum  when 
it  is  dissolved,  to  give  a  clear  solution,  as  well  as  to  form  ammo- 
nium chloride. 

DETERMINATION  OF  FERRIC  OXIDE  VOLUMETRICALLY. 
BY  POTASSIUM  PERMANGANATE. 

A  standard  solution  of  potassium  permanganate  is  required 
which  should  be  approximately  N/io.  Dissolve  6.4  grams  of 
pure  potassium  permanganate  in  about  400  c.c.  of  water,  warm 
slightly  to  assist  the  solution,  then  filter  through  a  layer  of  asbestos 
supported  by  a  cone  or  porcelain  plate  in  a  large  funnel  or  a  Gooch 
crucible ;  allow  the  solution  to  run  into  a  clean  dry  liter  flask ; 
wash  the  residue  on  the  asbestos,  hydrated  manganese  dioxide, 
with  water  and  then  dilute  the  permanganate  solution  in  the  flask 
to  the  delivery  mark  with  cold  distilled  water  (if  the  solution  is 
still  warm  allow  it  to  cool  to  the  temperature  for  which  the  flask 
was  graduated  and  make  up  the  contraction  by  more  water).  Pour 
the  contents  into  a  clean  dark  glass  bottle,  with  a  well-fitting 
ground-glass  stopper ;  fill  the  liter  flask  again  with  water  to  the 
delivery  mark  and  add  this  also  to  the  bottle  containing  the  per- 
manganate solution.  Mix  by  very  thorough  shaking  and  allow  to 
stand  several  hours  before  standardizing. 

The  warming  and  removal  of  the  dioxide,  which  is  formed  by 
organic  dust,  etc.,  by  filtration,  gives  a  solution  which  retains  its 
strength  better  than  if  this  process  goes  on  gradually  in  the  bottle. 

The  solution  must  be  filtered  through  asbestos  for  it  is  decom- 
posed by  filter  paper,  rubber  and  other  organic  materials.  If  an  old 
permanganate  solution  can  be  obtained,  it  will  remain  more  constant 
and  so  require  standardizing  less  frequently  than  a  freshly  made 
solution.  The  solution  obtained  will  be  nearly  Njio,  but  its 
strength  must  be  determined  by  experiments,  and  the  results 
should  not  differ  from  each  other  by  more  than  one  in  the  fifth 
place  ;  i.  e.y  0.00561  and  0.00562  is  the  greatest  error  allowable  in 
duplicates  for  the  value  of  I  c.c.  in  terms  of  iron.  Many  methods 
of  standardizing  have  been  proposed  *  of  which  three  will  be  men- 
tioned here. 

*Thiele  and  Deckert,  Z.  Angewandte  Chemiey  XIV.,  1233, 1901  ;  Dupr£  and  Muller, 
Z.  Angewandte  Chemie,  XV.,  1244,  1902  ;  Rust,  Z.  Analytische  Ckemie,  41,  606,  1902. 


FERRIC   AMMONIUM   ALUM.  33 

Iron  Wire  Method.  —  Take  a  spool  of  soft  iron  wire,  such  as  is 
used  by  florists,  and  remove  any  superficial  layer  of  oxide  by  emery 
paper  ;  this  will  then  be  very  close  to  99.7  per  cent.  iron.  The 
actual  iron  contents  can  be  determined  best  by  finding  the  percentage 
of  impurities  and  subtracting  it  from  one  hundred  per  cent.  Weigh 
out  two  portions  of  about  0.2  gram  each,  weighed  exactly  of  course, 
but  not  exactly  the  same  weight ;  place  these  in  two  250  c.c 
Erlenmeyer  flasks,  add  a  few  grams  of  sodium  bicarbonate  to 
each  and  then  about  100  c.c.  of  dilute  sulphuric  acid  (one  part  of 
concentrated  acid  to  five  of  water)  and  immediately  close  each  with  a 
rubber  stopper,  through  which  passes  a  bent  glass  tube  reaching  to 
the  bottom  of  a  beaker  of  distilled  water.  Heat  both  the  flask  and 
the  beaker  of  water  till  the  wire  has  completely  dissolved,*  best  on  a 
hot  plate  heated  by  gas,  then  turn  off  the  heat  and  allow  the  water 
in  the  beaker  to  be  drawn  back  so  that  it  almost  fills  the  Erlen- 
meyer flask. 

The  sodium  bicarbonate  is  added  so  that  carbon  dioxide  shall 
be  liberated  by  the  action  of  the  sulphuric  acid  which  will  replace 
the  air  in  the  flask.  The  water  seal  prevents  any  contact  with  the 
air  during  solution  so  that  the  iron  dissolves,  according  to  the  re- 
action Fe  +  H2SO4  =  FeSO4  -f  H2,  entirely  to  ferrous  sulphate, 
while  the  hydrogen  bubbles  up  through  the  water  in  the  beaker. 
The  water  in  the  beaker  is  heated  also  to  expel  the  air  dissolved 
in  it,  so  that  it  shall  be  free  from  oxygen  when  it  comes  in  contact 
with  the  ferrous  solution. 

There  is  one  situation  to  be  guarded  against,  if  attention  is  not 
given  and  the  water  is  not  allowed  to  run  over  soon  after  all  the 
iron  is  dissolved,  the  water  will  keep  on  evaporating  from  the 
flask  and  the  sulphuric  acid  become  concentrated  ;  then,  when  the 
hot  water  comes  in  contact  with  the  concentrated  sulphuric  acid 
an  explosion  ensues  which  destroys  the  determination  and  may  be 
dangerous  to  the  operator.  This  is  easily  avoided  by  preventing  the 
concentration  of  the  acid.  While  the  iron  is  dissolving  get  ready 
a  fifty  c.c.  burette,  which  has  been  found  to  be  accurately  graduated, 
fill  it  with  water  and  allow  it  to  run  out  to  see  whether  drops  ad- 
here to  the  sides  ;  if  they  do  clean  it  thoroughly  by  alcohol  or 
ether  to  remove  the  grease,  or  by  potassium  dichromate  and 
sulphuric  acid  ;  then  rinse  out  with  water  and  dry  by  alcohol 

*The  action  can  be  hastened  by  a  drop  of  hydrochloroplatinic  acid  solution. 


34  QUANTITATIVE   ANALYSIS. 

or  else  add  ten  c.c.  of  the  permanganate  solution,  shake  thor- 
oughly and  allow  the  solution  to  run  out  through  the  stopcock ; 
then  repeat  this  again  and  again,  so  that  the  burette  is  wet  with  a 
solution  so  nearly  the  strength  of  that  to  be  used  that  no  percep- 
tible dilution  results  when  the  burette  is  filled  with  the  permanga- 
nate solution. 

Fill  the  burette  and  adjust  to  the  zero  mark,  reading  the  top  of 
the  meniscus  with  this  dark  solution. 

Pour  the  ferrous  sulphate  solution  into  a  large  beaker,  and  rinse  out 
the  Erlenmeyer  flask  with  cold  distilled  water,  then  dilute  with  cold 
distilled  water  to  about  six  hundred  c.c.  and  the  solution  is  ready 
for  titration.  Run  in  the  permanganate  solution,  a  few  drops  at  a 
time,  till  the  pink  color  disappears  slowly,  then  drop  by  drop  till 
finally  one  drop  gives  a  pink  tinge  to  the  whole  solution,  which  is 
slight  but  perceptible  and  permanent.  Then  wait  for  two  minutes 
for  the  solution  on  the  sides  of  the  burette  to  run  down  and  for  the 
pink  color  to  disappear,  if  the  end  has  not  been  reached,  and  read 
the  volume  of  permanganate  used. 

Titrate  the  second  portion  of  iron  wire  the  same  way  and  com- 
pare the  results.  The  reaction  is 

ioFeS04+  2KMn04  +  8H2SO4=  sFe2(SO4)3 +  K2SO4 
4-  2MnSO4  +  8H2O. 

If  the  solution  should  turn  brown  it  is  a  sign  that  the  man- 
ganese is  not  being  reduced  completely  to  manganous  sulphate 
and  more  sulphuric  acid  must  be  added  at  once. 

Standardizing  by  Mohr's  Salt. —  Here  the  iron  is  already  in  the  fer- 
rous condition,  and  as  the  molecular  weight  is  large  —  about  seven 
times  that  of  the  iron  atom  —  any  error  in  weighing,  etc.,  is  only  one 
seventh  of  what  it  would  be  when  metallic  iron  is  used.  The  dis- 
advantage is  the  possibility  that  some  water  of  crystallization  has 
been  lost  so  that  the  salt  is  not  exactly  (NHj2SO4.FeSO4.6H2O. 
Select  crystals  which  have  no  white  appearance  at  the  edges  and 
weigh  out  quickly  two  portions  of  1-1.5  grams  each;  place  them 
in  large  beakers,  add  water  and  ten  c.c.  of  concentrated  sulphuric 
acid,  and  when  the  crystals  have  dissolved,  dilute  to  about  six 
hundred  c.c.,  add  more  sulphuric  acid  and  titrate  as  already  de- 
scribed. Calculate  the  results  and  compare  them  with  those 
obtained  with  the  wire.  Some  prefer  making  up  a  standard  so- 
lution of  the  ferrous  salt  and  measuring  this  out  from  a  second 


FERRIC  AMMONIUM  ALUM.  35 

burette,  but  separate  weighings  of  different  weights  are  preferable 
for  beginners  because  if  there  should  be  any  error  in  the  weight  of 
the  salt  taken  the  titration  results  would  check  though  the  stan- 
dard would  be  wrong  and  the  error  might  not  be  discovered  till 
much  later. 

Oxalic  acid  or  oxalates  may  be  used   for   standardizing.     The 
reaction  is 

5H2C204  +  2KMn04+  3H2SO4  =  ioCO2+  K2SO4 
+  2MnSO4  +  8H2O, 

which  takes  place  best  in  a  warm  solution  acid  with  sulphuric  acid. 
The  temperature  should  be  50-60°  C.  and  ten  grams  of  manga- 
nous  sulphate  should  be  added  to  make  the  reaction  take  place 
rapidly ;  the  end  point  is  the  same  permanent  pink,  but,  as  the  oxi- 
dation is  less  prompt  than  with  iron,  some  time  must  be  allowed, 
several  minutes,  to  oxidize  the  last  traces.  Here  if  we  weigh  out 
crystallized  oxalic  acid  we  have  the  doubt  as  to  whether  it  really 
is  H2C2O4.2H3O.  If  the  water  of  crystallization  is  right  the  method 
is  excellent.  (N  H4)2C2O.H2O,  KHC2O,.H2C2O4.2H2O  are  salts  fre- 
quently used  ;  also  lead  oxalate,  PbC2O4,  which  on  account  of  the 
high  atomic  weight  of  lead  and  the  absence  of  water  of  crystalliza- 
tion presents  theoretical  advantages. 

Determination  in  Ferric  Alum. — As  the  iron  in  the  alum  is  in  the 
ferric  condition  it  must  be  reduced  before  titration.  This  is  done 
most  conveniently  by  passing  the  solution,  acidified  with  sulphuric 
acid,  through  a  Jones  reductor.  The  simplest  form  of  this  ap- 
paratus consists  of  a  piece  of  glass  tubing  about  2  cm.  in  diameter 
and  at  least  40  cm.  long,  which  is  widened  at  the  top  like  a  funnel 
and  drawn  out  at  the  bottom  like  the  stem  of  a  funnel,  so  that  it 
will  pass  easily  through  the  hole  in  a  rubber  stopper.  A  perfor- 
ated platinum  cone  or  disc  of  platinum  is  placed  at  the  bottom  of 
the  wider  portion  and  on  this  a  plug  of  glass  wool,  about  8  mm. 
thick,  covered  by  a  thin  layer  of  asbestos  fiber ;  then  the  tube  is 
filled  nearly  to  the  top  with  granulated  zinc,  20-30  mesh  —  that 
which  will  pass  through  a  2O-mesh  sieve  but  not  through  a  30,  is 
the  best  size. 

The  zinc  is  amalgamated  as  follows  :  *  Dissolve  5  grams  of  mer- 
cury in  25  c.c.  of  nitric  acid,  1.2  sp.  gr.,  dilute  to  250  c.c.  and 
pour  into  a  large  flask ;  to  this  add  500  grams  of  granulated  zinc, 

*  Blair,  "Chemical  Analysis  of  Iron,"  p.  95,  etc. 


36  QUANTITATIVE   ANALYSIS. 

shake  thoroughly  for  two  minutes  and  then  pour  off  the  solution ; 
wash  the  zinc  repeatedly  with  water  and  fill  the  reductor  with  it. 
Weigh  out  two  portions  of  ferric  ammonium  alum,  about  2  grams 
each,  dissolve  these  in  about  100  c.c.  of  water  and  about  50  c.c.  of 
dilute  sulphuric  acid.  Place  the  reductor  through  the  rubber  stop- 
per of  a  stout  Erlenmeyer  flask  which  is  connected  by  a  side  tube 
with  the  suction.  Pour  the  solution  into  the  reductor  and  turn  on 
the  suction  gently,  adding  the  rest  of  the  solution  so  that  the  zinc 
is  always  covered.  As  the  ferric  solution  passes  through,  add  200 
c.c.  of  water  containing  10  c.c.  of  concentrated  sulphuric  acid 
and  then  follow  this  with  100  c.c.  of  water. 

The  solution,  assuming  its  volume  not  to  exceed  200  c.c.,  should 
require  at  least  four  minutes  to  pass  through  the  reductor.  The 
titration  can  be  made  directly  in  the  reductor  flask  after  dilution  if 
necessary,  as  already  described.  The  duplicates  should  agree 
closely  and  check  the  gravimetric  results  when  calculated  to  per- 
centage of  Fe2O3.  (The  permanganate  standard  is  in  terms  of  Fe.) 

The  length  of  the  column  of  zinc  should  be  at  least  35  cm.,  and 
when  freshly  filled  or  after  standing  some  time  it  should  be  washed 
with  dilute  sulphuric  acid.  Then  a  second  lot  of  dilute  sulphuric 
acid  should  be  run  through  and  this  titrated  with  permanganate. 
If  more  than  a  drop  is  required  to  color  the  solution,  the  amount 
must  be  determined  and  subtracted  from  the  subsequent  titrations. 
This  is  due  to  the  iron  which  is  usually  present  in  zinc  and  whose 
solution  may  not  have  been  entirely  prevented  by  the  amalgama- 
tion. 

If  air  is  allowed  to  pass  through  the  reductor  after  an  acid  solu- 
tion and  then  followed  by  acid  again,  hydrogen  peroxide  may  be 
formed,  which  uses  up  permanganate  according  to  the  reaction. 
5H202  +  2KMn04  +  3H2SO4  =  sO2+  K2SO4  +  2MnSO4+  8H2O, 
and  so  gives  too  high  results. 

This  method  can  also  be  applied  in  standardizing.  Dissolve  the 
iron  wire  by  dilute  sulphuric  acid  in  a  beaker  in  the  presence  of 
air,  then  run  the  solution  of  ferric  and  ferrous  sulphates  through 
the  reductor  and  titrate. 

The  permanganate  titration  depends  on  the  oxidation  of  the  iron 
present  from  the  ferrous  to  the  ferric  condition  by  a  solution  of 
known  oxidizing  power,  hence  any  other  oxidizing  or  reducing 
agents  which  would  affect  permanganate  must  be  absent.  Sul- 
phuric is  the  best  acid  to  use,  but  hydrochloric  is  permissible 
under  carefully  regulated  conditions. 


FERRIC  AMMONIUM   ALUM.  37 

BY  POTASSIUM  BICHROMATE. 

Make  up  a  solution  of  potassium  dichromate  containing  4.9 
grams  per  liter  and  standardize  it  as  follows  :  Weigh  out  at  least 
two  portions  of  clean  iron  wire  about  0.2  gram  each,  and  dissolve 
them  in  small  beakers  in  about  20  c.c.  of  hydrochloric  acid  i.i  sp. 
gr.;  rinse  down  the  cover  and  sides  of  the  breaker  and  while  still  hot 
add  drop  by  drop  from  a  pipette  a  very  dilute  and  strongly  acid 
solution  of  stannous  chloride  until  the  solution  becomes  colorless  ; 
then  dilute  to  about  50  c.c.  and  add  at  once  10  c.c.  of  a  saturated 
solution  of  mercuric  chloride,  which  should  give  a  white  silky  pre- 
cipitate of  mercurous  chloride ;  pour  this  solution  into  distilled 
water  containing  20  c.c.  of  concentrated  hydrochloric  acid  and 
dilute  to  about  600  c.c.  Place  on  a  porcelain  tile  or  plate  some 
drops  of  a  very  dilute  and  freshly  prepared  solution  of  potassium 
ferricyanide.  Run  in  the  dichromate  solution  until  nearly  the 
calculated  quantity  has  been  added,  then  after  stirring,  remove  a 
drop  and  place  it  in  contact  with  a  drop  of  ferricyanide  on  the 
plate.  A  blue  color  will  result  due  to  the  reaction  between  the  ferri- 
cyanide and  the  ferrous  iron  still  present ;  continue  adding  dichro- 
mate from  the  burette  until  no  blue  coloration  is  produced  with  a 
drop  of  the  indicator.  Treat  the  second  portion  in  the  same  way 
and  calculate  the  standard  of  the  solution  in  terms  of  iron.  The 
results  should  agree  as  closely  as  in  the  permanganate  titration. 
The  reaction  of  titration  is : 

6FeCl2  +  K2C207  +  I4HC1  =  6FeQ3  +  2KC1  -f  2CrQ3  +  ;H2O 
and  for  the  blue  color, 

3FeCl2  +  2K3Fe(CN)6  =  Fe3(Fe(CN)6)2  -f  6KC1. 

The  special  precautions  to  be  observed  are :  To  keep  the  solu- 
tion concentrated,  hot  and  strongly  acid  when  reducing  by  stan- 
nous chloride  and  to  avoid  an  excess  of  more  than  one  drop.  If 
the  solution  is  cold,  dilute  or  insufficient  hydrochloric  acid  is  pres- 
ent, the  reduction  is  slow  and  an  excess  of  stannous  chloride  is 
added  before  the  solution  becomes  colorless ;  then  when  the  mer- 
curic chloride  is  added  a  black  precipitate  of  finely  divided  mer- 
cury results,  which  destroys  the  determination  as  it  is  likely  to  be 
oxidized  by  the  potassium  dichromate. 

The  reactions  are :  Fe  +  2HC1  =  FeCl2+  H2;  2FeCl2+  2HC1+  O 
(from  the  air)  =  2FeCl3+H2O;  2FeCl3+  SnCl3=  2FeCl2-f  SnCl4  and 


QUANTITATIVE    ANALYSIS. 

with  the  excess  of  stannous  chloride,  SnCl2+  2HgCl2  =  SnCl4  + 
Hg2Cl2.  If  the  excess  of  stannous  chloride  is  too  great  we  get 
SnCl2  +  Hg2Cl2  =  SnCl,+  2Hg. 

The  10  c.c.  of  mercuric  chloride  solution  should  be  added  at 
once  to  get  it  in  excess  as  regards  the  stannous  chloride  as  quickly 
as  possible  and  so  avoid  the  last  reaction.  The  indicator  must  be 
free  from  ferricyanide,  for  if  this  is  present  we  get  a  blue  with  the 
ferric  salt  as  well,  and  so  no  end  point.  It  should  for  this  reason 
be  made  up  by  dissolving  a  crystal  the  size  of  a  pin  head  in  water 
in  a  small  watch  glass ;  if  more  concentrated,  the  brown  coloration 
due  to  ferric  ferricyanide  may  mask  the  blue.  When  properly 
carried  out  the  end  point  is  extremely  sensitive. 

To  determine  the  iron  in  the  alum,  weigh  out  two  portions  of 
about  2  grams  each  and  dissolve  in  hydrochloric  acid  I  :  I  using 
30-40  c.c.  and  heating ;  then  reduce  by  stannous  chloride,  using 
more,  of  course,  than  with  the  wire,  and  carry  out  the  operation  just 
as  in  standardizing. 

This  method  has  many  advantages  :  first,  it  is  extremely  ac- 
curate; second  ,it  can  be  done,  and  is  best  done,  in  a  hydrochloric 
acid  solution  which  is  the  best  solvent  for  iron  in  ores ;  third,  the 
reduction  by  stannous  chloride  is  very  rapid  and  at  the  same  time 
does  not  reduce  the  titanic  chloride  often  present  from  magnetites, 
while  zinc  reduces  this  to  TiCl,,  which  is  reoxidized  by  perman- 
ganate giving  too  high  results. 

The  disadvantage  is  the  outside  indicator  which  is  tiresome 
and  may  cause  inaccuracy  when  too  many  drops  are  removed. 
It  is  evident  that  this  solution  may  be  standardized  by  Mohr's  salt 
but  not  by  oxalic  acid  or  oxalates  as  there  would  be  no  end  point. 


ANALYSIS    OF    IRON    ORE.  39 


CHAPTER   VI. 

Analysis  of  Iron  Ore. 

Under  this  title  the  complete  analysis  of  all  iron  ores  might  be 
considered,  and  then  the  determination  of  most  of  the  known  ele- 
ments would  be  involved  as  they  are  occasional  constituents  of 
iron  ores.  However  as  this  is  not  often  required  of  the  chemist, 
only  the  determinations  of  greatest  technical  importance  will  be 
given  in  detail,  namely,  iron,  silica,  sulphur  and  phosphorus. 
When  only  a  partial  analysis  is  made,  the  iron  is  most  easily  deter- 
mined in  separate  portions,  while  a  larger  quantity  is  taken  for  the 
determination  of  silica,  sulphur  and  phosphorus. 

DETERMINATION  OF  IRON. 

By  Potassium  Bichromate.  Penny  s  Method.  —  Grind  about  a 
gram  of  the  sample  in  an  agate  mortar  till  it  feels  like  flour,  from 
this  weigh  out  two  portions  of  about  0.35  gram  each  and  treat 
them  in  small  beakers  with  from  one  to  three  c.c.  of  stannous 
chloride  solution  (250  grams  per  liter),  depending  on  the  amount 
of  iron  oxide  present,  and  20  c.c.  of  hydrochloric  acid,  i.i  sp.  gr. 
The  beakers  should  be  covered  and  heated  on  a  hot  plate  for  from 
ten  to  fifteen  minutes,  until  the  residues  are  white  or  until  no 
further  solution  can  be  effected .  In  most  cases  complete  solution 
of  the  iron  takes  place  readily  if  the  ore  is  ground  to  an  impalpable 
powder  but  with  some  ores,  particularly  magnetites,  pyroxene  and 
other  insoluble  silicates  containing  iron  may  be  present,  which 
require  a  fusion  with  sodium  carbonate,  etc.,  to  obtain  all  the  iron 
from  the  greenish  residue. 

(a]  The  residue  is  white,  the  solution  may  be  either  colorless 
or  yellow;  if  it  is  colorless,  an  excess  of  stannous  chloride  has 
been  added,  which  must  be  destroyed  by  adding  potassium  per- 
manganate or  hydrogen  peroxide  till  the  solution  becomes  yellow, 
otherwise  a  black  precipitate  of  mercury  would  be  formed  in  the 
next  operation.  Rinse  down  the  sides  of  the  beaker  and  the  cover 
and  while  the  solution  is  still  hot  add  drop  by  drop  a  very  dilute 
solution  of  stannous  chloride  until  the  iron  is  reduced,  then  dilute 
to  about  50  c.c.  and  add  10-12  c.c.  of  a  saturated  solution  of  mer- 


40  QUANTITATIVE   ANALYSIS. 

curie  chloride  as  already  described,  and  continue  the  titration  as 
under  iron  alum. 

(£)  If  the  residue  is  greenish  filter  it  off  and  titrate  the  soluble 
iron.  Fuse  the  residue  with  at  least  six  times  its  weight  of  potas- 
sium and  sodium  carbonates  *  in  a  platinum  crucible  for  half  an 
hour,  using  a  blast  lamp  if  necessary  to  obtain  a  clear  fusion  ;  dis- 
solve the  melt  in  hydrochloric  acid  and  water  and  filter  out 
any  flocculent  silica,  washing  it  with  hot  water  ;  to  the  filtrate 
add  an  excess  of  ammonia,  filter  out  the  impure  ferric  hydroxide 
and  wash  it  twice  with  hot  water ;  dissolve  through  the  filter  by 
hot  dilute  hydrochloric  acid  into  a  No.  I  beaker,  reduce  by  stan- 
nous  chloride,  add  mercuric  chloride  and  titrate  as  usual  by 
potassium  dichromate.  Calculate  the  percentage  of  iron  from 
the  total  quantity  of  dichromate  used.  It  might  seem  that  the 
hydrochloric  acid  solution  of  the  fusion  could  be  reduced  at  once 
for  titration,  but  there  are  two  objections  :  first,  in  the  presence  of 
the  alkali  chlorides,  double  salts  with  mercury  are  formed  which 
are  easily  reduced,  so  that  a  black  precipitate  of  mercury  almost 
invariably  results.  Second,  very  often  in  reducing  by  stannous 
chloride  the  color  will  become  darker  instead  of  lighter.  This  is 
due  to  the  formation  of  platinous  chloride  from  the  crucible  which 
gives  a  very  intense  color,  similar  to  ferric  chloride,  but  which 
passes  into  the  filtrate  when  the  iron  is  precipitated  by  ammonia. 

If  exactly  fifty  times  the  standard  of  the  solution  is  taken,  twice 
the  number  of  cubic  centimeters  used  is  the  percentage  of  iron 
without  further  calculation. 

By  Potassium  Permanganate  —  Zimmerman- Remhart  Method.\  — 
Treat  the  ore  as  for  the  preceding  method  up  to  the  point  where 
the  silky  precipitate  of  mercurous  chloride  is  obtained,  being  care- 
ful that  not  more  than  15  c.c.  of  hydrochloric  acid  I  :  I  is  present. 
Pour  this  into  500-600  c.c.  of  cold  water  to  which  8-10  c.c.  of 
"  preventive  "  solution  has  been  added,  and  titrate  by  permanga- 
nate as  usual,  except  that  the  end  point  is  not  a  pink  which  lasts 
for  several  minutes,  but  the  first  tinge  of  pink  which  colors  the 
the  solution  and  then  fades  away  in  a  few  seconds. 

The  ''preventive"  solution  is  made  by  dissolving  160  grams  of 
manganous  sulphate  in  1750  c.c.  of  water,  then  adding  330  c.c.  of 

*  These  are  mixed  in  molecular  proportions,  as  this  mixture  is  more  easily  fusible 
than  either  alone. 

f  Mixer  and  Dubois,  J.  Am.  C.  S.,  17,  405. 


ANALYSIS   OF   IRON    ORE.  41 

phosphoric  acid  1.7  sp.  gr.  (syrupy)  and  320  c.c.  of  sulphuric  acid 
1.82  sp.  gr. 

This  is  the  neatest  and  most  rapid  method  for  the  determina- 
tion of  iron  in  ores  and  is  very  accurate  when  properly  carried  out. 

We  saw  that  if  hydrochloric  acid  is  present  in  considerable 
quantity,  especially  in  a  hot  solution,  that  titration  by  permanga- 
nate was  impossible,  as  the  hydrochloric  acid  was  oxidized  with  the 
liberation  of  chlorine  ;  so  the  amount  of  hydrochloric  acid  present 
must  be  small,  not  over  10  c.c.  of  concentrated  acid  in  a  bulk  of 
500  to  600  c.c.,  and  the  solution  cold. 

The  effect  of  the  "  preventive "  solution  is  as  follows :  The 
manganous  sulphate  acts  as  a  sort  of  carrier  of  oxygen,  it  is 
changed  to  the  manganic  condition  by  any  chlorine  which  may 
be  formed  and  this  in  turn  is  reduced  by  the  ferrous  salt  back  to 
the  manganous  condition  *  and  so  does  away  with  the  bad  effect 
of  hydrochloric  acid  when  it  is  present  in  not  too  large  amount. 

The  sulphuric  and  phosphoric  acids  give  acidity  and  sharpen 
the  end  point  by  giving  a  colorless  solution  at  the  end  due  to  the 
preponderance  of  ferric  sulphate  and  phosphate  instead  of  chloride. 

It  is  important  to  carry  out  this  method  exactly  as  described, 
even  slight  variations  are  usually  disastrous ;  for  example,  if  the 
preventive  solution  is  added  to  the  ferrous  solution  in  the  small 
beaker,  instead  of  to  the  water  used  for  dilution  or  else  after  dilu- 
tion, the  silky  precipitate  is  decomposed  into  mercurous  sulphate 
which  may  then  give  mercuric  sulphate  and  mercury  and  so  spoil 
the  determination. 

When  there  is  an  insoluble  residue  it  is  treated  as  described 
under  Penny's  method  and  the  solutions  combined  or  else  titrated 
separately. 

When  a  complete  analysis  of  an  iron  ore  is  made,  it  may  be 
more  convenient  to  precipitate  the  iron  together  with  aluminum 
hydroxide  and  phosphoric  acid  in  an  aliquot  part  of  the  solution. 
This  precipitate  can  be  treated  by  any  of  the  methods  given  for 
the  ferric  alum  or  for  the  ore.  If  titanium  should  be  present  it 
will  contaminate  the  ammonia  precipitate  and  in  this  case  reduc- 
tion by  stannous  chloride,  sulphurous  acid  or  hydrogen  sulphide 
must  be  used. 


*  Comparable  with  the  action  of  the  oxides  of  nitrogen  in  the  manufacture  of  sul- 
phuric acid. 


42  QUANTITATIVE   ANALYSIS. 

SCHEME  FOR  THE  DETERMINATION  OF  SILICA,  SULPHUR  AND 
PHOSPHORUS  IN  ONE  PORTION. 

Weigh  out  5  grams  of  the  ore  ground  fine  in  an  agate  mortar ; 
heat  with  50  c.c.  concentrated  hydrochloric  acid  and  7-8  c.c.  con- 
centrated nitric  acid,  to  prevent  loss  of  sulphur  as  hydrogen 
sulphide,  in  a  beaker  for  about  fifteen  minutes  ;  dilute,  heat  again 
and  filter  hot;  wash  the  residue  twice  with  dilute  hydrochloric 
acid.  Place  the  filtrate  in  a  casserole  to  evaporate  on  a  hot  plate 
or  steam  bath,  with  a  watch  glass  over  it  raised  to  allow  the  escape 
of  steam  by  a  glass  rod  triangle.  Burn  the  paper  containing  the 
residue  in  a  platinum  crucible,  add  to  it  at  least  six  times  its  weight 
of  mixed  carbonates  and  a  small  crystal  (about  0.2  gram)  of  sodium 
nitrate ;  mix  thoroughly  with  a  stout  platinum  wire  or  dry  glass 
rod,  being  careful  not  to  lose  any,  and  fuse  for  half  to  three  quarters 
of  an  hour  over  a  Bunsen  burner,  then  for  10-15  minutes  over  a 
blast  lamp.  Allow  the  melt  to  cool  and  remove  it  from  the  crucible 
in  a  cake  if  possible.  Place  this  in  a  small  casserole,  then  cover  it 
with  concentrated  hydrochloric  acid  and  regulate  the  rate  of  solu- 
tion by  adding  water;  add  the  solution  of  what  remains  in  the 
crucible  dissolved  in  dilute  hydrochloric  acid ;  heat  to  boiling  and 
boil  till  everything  has  dissolved,  except  possibly  some  white 
hydrated  silica.  There  should  be  no  dark  or  gritty  particles  left, 
as  these  show  incomplete  decomposition  of  the  ore  and  require 
refusion.  If  the  decomposition  is  complete  add  this  solution  to 
the  first  solution  of  the  ore  (which  has  been  evaporating)  and 
evaporate  to  dryness;  when  nearly  dry  stir  so  as  to  form  irregular 
granular  masses,  which  present  a  large  surface  and  hasten  the  sub- 
sequent dehydration.  Place  in  an  air-bath  (covered)  and  heat  at 
II5°-I2O°  C.,  until  no  odor  of  hydrochloric  acid  is  perceptible. 
If  the  ore  is  very  siliceous  moisten  it  again  with  hydrochloric  acid 
and  repeat  this  treatment.  Add  15-20  c.c.  of  concentrated  hydro- 
chloric acid  and  heat  to  dissolve  the  basic  ferric  salts ;  then  dilute 
with  water  and  heat  to  boiling ;  filter  out  the  silica  which  has  been 
rendered  insoluble  by  dehydration  and  wash  alternately  with  hot 
dilute  hydrochloric  acid  and  cold  water,  then  with  water  till  free 
from  chlorides.  Burn  the  paper  containing  the  silica  in  a  weighed 
platinum  crucible,  ignite  finally  over  a  blast  lamp,  cool  in  a  des- 
iccator and  weigh.  To  make  sure  of  the  purity  of  the  silica  drive 
it  off  as  silicon  fluoride,  SiF4,  adding  first  a  few  drops  of  dilute 


ANALYSIS   OF   IRON   ORE.  43 

sulphuric  acid  to  hold  back  any  titanic  oxide  and  then  adding 
hydrofluoric  acid  and  warming  gently  on  an  asbestos  pad,  and 
finally  igniting  strongly.  If  any  residue  is  left  repeat  this  treat- 
ment till  a  constant  weight  is  obtained. 

If  there  should  be  a  residue,  it  is  likely  to  be  alumina,  titanic 
oxide  or  barium  sulphate,  with  possibly  traces  of  iron,  and  in  the 
present  case  can  be  neglected  unless  barium  sulphate  or  titanic- 
oxide  are  present ;  the  first  because  we  are  to  determine  the  total 
sulphur,  the  second  because  it  may  carry  down  phosphoric  acid 
with  it.  In  either  event  fuse  this  residue  and  leach  out  the  fusion 
with  water  (no  acid,  or  barium  sulphate  would  reform)  filter  and 
add  the  filtrate  to  the  main  solution.  If  a  fine  white  precip- 
itate should  be  formed  at  this  point  while  the  solution  is  still 
acid,  it  will  be  barium  sulphate  due  to  the  presence  of  more  than 
enough  barium  in  the  ore  to  combine  with  the  sulphate  and  must 
be  filtered  out  and  added  to  any  barium  sulphate  found  as  usual.* 

Pour  the  main  solution  into  an  excess  of  ammonia  diluted  with 
water  in  a  large  beaker,  heat,  filter  and  wash  first  by  decantation 
and  then  on  the  filter  with  hot  water  till  free  from  chlorides. 
Evaporate  the  filtrate  down  to  about  200  c.c.,  acidify  and  precipi- 
tate the  sulphur  as  barium  sulphate  using  the  conditions  given 
under  coal  analysis. 

Treatment  of  Precipitate  containing  iron,  aluminum  and  phos- 
phoric acid,  also  in  some  cases  manganese,  titanium,  chromium, 
arsenic,  etc.  Transfer  as  much  as  possible  of  the  precipitate  to  a 
No.  3  or  4  beaker  and  place  it  under  the  funnel,  pour  through  the 
paper  hot  dilute  nitric  acid  till  all  the  adhering  precipitate  is  dis- 
solved, allowing  the  solution  to  run  into  the  beaker  containing  the 
bulk  of  the  precipitate,  add  more  nitric  acid  and  heat  till  the  pre- 
cipitate has  dissolved,  neutralize  with  ammonia  till  the  solution  is 
deep  red  in  color  but  clear,  then  add  nitric  acid  again  till  the 
red  color  is  just  changed  to  orange,  add  ten  grams  of  ammonium 
nitrate  and  warm  the  solution  to  about  60°  C.,  add  100  c.c.  of 
molybdate  solution,  and  allow  to  stand  for  half  an  hour  at  a  tem- 
perature of  about  45 °  C.  If  the  operation  is  to  be  hastened  the 
precipitation  can  be  done  in  a  flask  and  shaken  for  five  minutes, 
wrapped  in  a  towel  to  prevent  cooling,  then  allowed  to  stand  for 
another  five  minutes  and  the  precipitation  will  be  complete,  unless 
the  amount  of  phosphorus  present  is  only  o.oi  per  cent,  or  less.  Fil- 

*  The  precipitation  may  not  be  complete  on  account  of  the  acidity  of  the  solution. 


44  QUANTITATIVE   ANALYSIS. 

ter  and  wash  with  water  to  which  I  per  cent,  nitric  acid  and  10  per 
cent,  ammonium  nitrate  have  been  added  until  the  washings  give 
no  brown  coloration  with  hydrogen  sulphide,  showing  the  com- 
plete removal  of  molybdenum. 

The  molybdate  reagent  is  made  as  follows:  100  grams  of 
molybdic  anhydride  (MoO3)  are  mixed  with  400  c.c.  of  distilled 
water  and  80  c.c.  of  strong  ammonia  added,  the  solution  of  am- 
monium molybdate  is  filtered,  to  remove  silica  and  dust,  and  poured 
a  little  at  a  time,  into  a  mixture  of  300  c.c.  of  nitric  acid  1.42  sp.  gr. 
and  700  c.c.  of  water;  then  one  c.c.  of  a  ten  per  cent,  solution  of 
sodium  phosphate  is  added  to  saturate  the  soluton  with  the  "  yel- 
low precipitate  "  and  the  reagent  is  allowed  to  stand  over  night. 
The  nitric  acid  must  not  be  poured  into  the  molybdate  as  it  will 
give  a  separation  of  molybdic  acid  near  the  neutral  point  which  is 
difficult  to  redissolve.  For  the  same  reason  the  ammonium  molyb- 
date should  not  be  added  to  the  nitric  acid  all  at  once  on  account 
of  the  heat  produced  in  the  neutralization. 

We  have  now,  the  yellow  crystalline  ammonium  phospho-molyb- 
date,  (NH4)3PO4  i2MoO3, washed  free  from  molybdenum  andiron; 
dissolve  this  in  100  c.c.  of  dilute  ammonia  (i  part  0.9  sp.  gr.  to  10 
of  water)  nearly  neutralize  with  hydrochloric  acid,  and  add  slowly, 
not  faster  than  10  c.c.  a  minute,  with  stirring  an  excess  of  "  mag- 
nesia mixture."  The  amount  is  judged  by  the  quantity  of  the 
"yellow  precipitate"  and  should  be  I  c.c.  for  every  10  mgs.  of 
phosphorus  pentoxide  present.  The  "  magnesia  mixture  "  is  made 
by  dissolving  55  grams  of  magnesium  chloride  and  70  grams  of 
ammonium  chloride  in  a  liter  of  dilute  ammonia,  I  to  10.  After 
stirring  briskly  add  about  8  c.c.  of  strong  ammonia.  The  precipi- 
tate is  allowed  to  stand  in  the  cold  for  at  least  four  hours  filtered, 
washed  with  ammonia  (i  :  10,  containing  about  2.5  per  cent.  NH3) 
ignited  as  already  described,  heated  with  the  blast  lamp  and 
weighed.  The  percentages  of  sulphur  and  phosphorus  are  reported 
in  an  iron  ore,  not  the  percentages  of  SO3  and  P,O5. 

NOTES,  REASONS  AND  PROPERTIES  OF  PRECIPITATES. 
Some  authorities  recommend  the  fusion  of  the  entire  five  grams 
to  begin  with.  There  are  two  important  objections :  First,  the 
cost  of  the  platinum  crucible  large  enough  to  do  it  in  ;  second,  the 
introduction  of  30-35  grams  of  alkali  chloride  into  the  solution 
at  the  start  which  interferes  with  clean  separations  and  makes 
longer  washing  necessary. 


ANALYSIS    OF   IRON    ORE.  45 

The  dehydration  of  silica  is  an  operation  of  the  greatest  impor- 
tance in  analytical  chemistry  and  is  usually  the  first  step  after 
solution  is  obtained.  If  the  silica  is  not  removed  completely  and 
at  once  it  comes  down  gradually  and  contaminates  the  subsequent 
precipitates.  Then  we  do  not  know  whether  the  silica  which  may 
contaminate  the  Mg2P2O7  precipitate  is  from  the  ore  or  from  the 
action  of  the  solutions  on  the  beakers.  Ores  contain  silica  as 
quartz  and  as  silicates  of  lime,  magnesia,  iron,  etc.  Some  of  these  are 
soluble  and  others  are  not,  depending  on  the  particular  minerals, 
so  that  the  original  solution  of  the  ore  may  contain  silica  in  solu- 
tion and  the  residue  insoluble  silicates  besides  silica ;  when  fused 
with  alkali  carbonates  these  give  soluble  alkali  silicates  which  on 
acidifying  give  silicic  acids.  The  evaporation  and  baking  drives  the 
water  off  these  silicic  acids,  H2SiO3,  H4SiO4,  etc.,  giving  when  dried 
at  about  100°  SiO2iH2O  which  is  nearly  insoluble.  This  we  filter  out, 
but  it  must  be  heated  by  a  blast  lamp  before  weighing  to  drive  off 
the  last  half  molecule  of  water.  It  is  not  to  be  inferred  that  one 
evaporation  is  sufficient  to  effect  an  absolutely  complete  separation 
of  silica,  although  it  usually  suffices  for  iron  ores.  Care  must  be 
taken  not  to  allow  the  temperature  to  go  above  1 20°  as  there  is 
danger  of  the  reformation  of  silicates  above  I4O°C.,  particularly  if 
magnesium  is  present. 

Conditions  for  Precipitating  the  Ammonium  Phosphomolybdate. — 
The  solution  should  be  slightly  acid  with  nitric  acid  and  contain 
20  grams  of  ammonium  nitrate,  no  tartrates  or  other  organic  com- 
pounds, and  preferably  no  chlorides  or  sulphates.  The  acidity 
is  of  great  importance ;  if  too  acid,  the  precipitation  is  slow  and 
often  incomplete ;  if  too  near  the  neutral  point,  the  separation  from 
iron  is  incomplete,  and  reddish  crusts  containing  iron  may  form. 
These  are  insoluble  when  the  phosphomolybdate  is  dissolved  in 
ammonia,  but  may  retain  phosphorus  and  must  be  dissolved  in  nitric 
acid  and  the  phosphorus  reprecipitated  as  ammonium  phospho- 
molybdate. In  regard  to  temperature ;  if  too  hot  (85°  or  over),  or 
if  allowed  to  stand  for  a  long  time,  the  precipitate  is  liable  to  be 
contaminated  by  the  separation  of  molybdic  acid ;  if  too  cold,  say 
20°  C.,  the  precipitation  is  slow.  The  best  temperature  is  about 
45°  C.,  for  the  reasons  given,  and  also  on  account  of  arsenic. 
When  this  is  present  and  the  temperature  is  high  an  arsenio-mo- 
lybdate  similar  in  composition  to  the  phospho-molybdate  separates 
and  gives  too  high  results,  as  it  forms  with  magnesia  mixture  an 


46  QUANTITATIVE   ANALYSIS. 

insoluble  magnesium  ammonium  arsenate  similar  to  the  magne- 
sium ammonium  phosphate.  Reducing  agents  and  silica  should 
be  absent ;  the  latter  comes  down  as  hydrated  silica,  but  not  as  a 
silicomolybdate. 

Solubility  of  Ammonium  Phospho-molybdate.  —  Readily  soluble  in 
ammonia  and  other  alkalies,  in  alkali  phosphates ;  soluble  in  hydro- 
chloric acid,  strong  sulphuric  and  nitric  acids  ;  very  slightly  soluble 
in  water.  Best  washed  with  I  per  cent,  nitric  acid  and  10  per  cent, 
ammonium  nitrate,  or  I  per  cent,  sulphuric  acid  and  10  per  cent, 
ammonium  sulphate. 

There  is  no  longer  any  doubt  as  to  the  composition  of  this  pre- 
cipitate when  formed  under  the  conditions  given,  though  it  may 
carry  down  with  it  somewhat  uncertain  but  relatively  small  quan- 
tities of  nitric  acid  and  water  of  crystallization.  When  carefully 
precipitated  it  may  be  dried  for  half  an  hour  at  I2O°C.  and 
weighed  ;  it  then  contains  1.63  per  cent,  of  phosphorus. 

In  dissolving  the  precipitate  very  dilute  ammonia  is  used  for 
two  reasons:  (i)  that  ammonium  molybdate  is  not  very  soluble  in 
ammonia,  (2)  to  avoid  a  great  excess  of  ammonium  chloride  in  the 
subsequent  precipitation. 

Magnesium  Ammonium  Phosphate  can  be  obtained  under  three 
different  conditions,  according  to  Neubauer. 

1.  The  precipitate  is  formed  in  a  neutral  or  ammoniacal  solu- 
tion containing  no  excess  of  magnesium  salt.     Result,  the  precipi- 
tate contains  less  than  the  normal  amount  of  magnesium  and  phos- 
phorus pentoxide  is  volatilized  on  ignition.     Results  low. 

2.  The  precipitate  formed  is  in  the  presence  of  an  excess  of 
magnesium  salt  but  during  its  formation  ammonia  is  not  present 
in  large  excess.     Results  correct. 

3.  The  precipitate  is  formed  in  the  presence  of  an  excess  of 
both  magnesium  and  ammonia.     Results  high. 

The  other  precautions  in  regard  to  treating  this  compound  have 
been  given  under  magnesium  sulphate. 

There  is  no  advantage  in  using  separate  portions  for  sulphur  or 
phosphorus  as  they  may  not  be  entirely  soluble  in  acids  so  that 
when  the  silica  is  removed  no  time  is  saved.  The  insoluble  phos- 
phorus is  supposed  to  be  combined  with  aluminum  and  can  be 
rendered  soluble  by  a  strong  ignition  previous  to  treating  with 
acids. 


ANALYSIS    OF   IRON    ORE.  47 

ADDITIONAL  REFERENCES. 

MIXER  AND  Du  Bois.     Notes  on  the  Determination  of  Insoluble 

Phosphorus  in  Iron  Ores.     Trans.  Am.  I.  M.  E.,  Feb.,  1897. 
BASKERVILLE.     On    the    Analysis    of    Titaniferous    Iron     Ores. 

Journal  of  the  Soc.  of  Chemical  Industry,  19,  419. 
POPE.     Investigation  of  the  Titaniferous  Magnetites,  etc.     Trans. 

Am.  I.  M.  E.,  29, 372. 
WALLER.     Analysis  of  Chrome  Ores.     J.  Soc.  Chem.  Industry, 

15,436. 


48  QUANTITATIVE   ANALYSIS. 


CHAPTER  VII. 
Pig  Iron  and  Steel  Analysis. 

DETERMINATION  OF  PHOSPHORUS. 

The  phosphorus  in  iron  or  steel,  unlike  that  in  ores,  exists  as  a 
phosphide,  so  the  first  step  in  the  analysis  is  an  oxidizing  treatment, 
solution  in  nitric  acid,  with  this  exception  the  method  given  for 
iron  ore  can  be  applied  to  steel  and  to  pig  iron  after  filtering  off  the 
graphite,  etc.;  but  the  method  is  too  long  for  the  demands  of  a 
metallurgical  plant  and  the  "  permanganate  method  "  is  very  gen- 
erally used.  This  method  has  many  slight  variations  but  the 
essential  features  are  always  the  same.  The  following  description 
most  nearly  approaches  the  methods  of  W.  A.  Noyes  and  of  Blair. 

Reagents:     Nitric  acid,  1.18  sp.  gr. 

Permanganate  solution,  12.5  grams  per  liter. 

Ferrous  sulphate  in  fine  crystals  free  from  phosphorus  (Baker 
and  Adamson). 

Ammonia,  cone.  0.9  sp.  gr.;  dilute  0.96  sp.  gr. 

Molybdate  solution  as  described  under  iron  ore. 

Washing  solution :  Acid  ammonium  sulphate,  made  by  adding 
27.5  c.c.  of  dilute  ammonia  (0.96  sp.  gr.)  and  24  c.c.  of  concen- 
trated sulphuric  acid  to  water  and  diluting  to  one  liter. 

The  standard  permanganate  already  described. 

Methods :  Weigh  out  2  grams  of  steel  or  1-2  grams  of  pig  iron  ; 
place  in  a  500  c.c.  flask;  add  50  c.c.  nitric  acid  (1.18  sp.  gr.)  and 
warm  gently  till  solution  is  complete,  then  boil  for  a  minute  (with 
pig  irons  there  will  remain  a  black  residue  of  graphite),  add  10  c.c. 
of  the  strong  permanganate  solution  and  boil  till  the  pink  color 
disappears.  The  permanganate  is  added  to  complete  the  oxidation 
of  the  phosphorus  which  must  be  present  entirely  as  an  ortho- 
phosphate  in  order  to  be  precipitated  as  phosphomolybdate.  On 
boiling,  the  manganese  separates  from  the  permanganate  as  hy- 
drated  dioxide.  This  is  cleared  up  by  a  reducing  agent  free  from 
phosphorus,  i.  e.,  ferrous  sulphate,  added  in  small  portions  till  the 
solution  clears,  (with  pig  iron  the  graphite  remains).  At  this  point, 
with  pig  irons,  it  is  best  to  filter  out  the  graphite,  etc.,  so  as  to  have 
a  clear  solution  for  the  precipitation  of  the  phosphomolybdate  and 


PIG   IRON   AND    STEEL   ANALYSIS.  49 

also  to  save  time  in  the  filtering  and  washing.  Cool  to  about  50°  C. 
and  add  8  c.c.  *  of  strong  ammonia  water  for  a  steel,  slightly  more 
for  a  pig  iron,  if  only  a  gram  is  taken.  Insert  a  rubber  stopper  and 
shake  till  the  precipitate  of  ferric  hydroxide  and  phosphate  redis- 
solves.  Cool  or  warm"  the  solution  until  it  is  as  many  degrees 
above  or  below  60°  is  the  molybdate  solution  is  below  or  above 
27°  C.  (so  that  when  mixed  the  temperature  will  be  approximately 
45°  C.).  Add  60  c.c.  of  the  molybdate  reagent,  insert  the  stopper, 
wrap  in  a  towel  to  prevent  cooling  and  shake  vigorously  for  five 
minutes,  allow  to  settle  for  five  minutes  and  filter  through  a  9  cm. 
paper.  Wash  from  the  top  down  with  the  acid  ammonium  sulphate 
solution  until  5  c.c.  give  no  brown  coloration  with  hydrogen  sulphide 
water  (showing  the  complete  absence  of  molybdenum).  Pour  over 
the  precipitate  12  c.c.  of  ammonia  (0.96  sp.  gr.)  diluted  to  25  c.c.  and 
allow  the  solution  to  run  into  the  precipitation  flask.  Wash  with  100 
c.c.  water,  then  add  80  c.c.  more  water  and  10  c.c.  of  cone,  sul- 
phuric acid.  Pass  this  solution  through  a  Jones  reductor,  with  the 
precautions  already  described  under  ferric  alum,  follow  it  with  200 
c.c.  of  water  and  titrate  the  solution  at  once  in  the  reductor  flask 
without  dilution  or  delay. 

Notes.  —  This  method  is  entirely  satisfactory  for  steels  and,  with 
the  modifications  given,  works  well  for  pig  irons  ;  it  is  not  certain 
whether  it  is  accurate  for  spiegel  or  for  some  special  steels  contain- 
ing chromium,  tungsten,  molybdenum, etc.,  and  should  be  checked 
up  by  the  gravimetric  method  when  used  on  such  samples. 

With  pig  iron  the  amount  of  ammonia  to  be  used  in  neutralizing 
varies  and  in  all  cases  some  judgment  must  be  used  and  the  cor- 
rect degree  of  acidity  obtained.  When  only  o.oi  per  cent,  of  phos- 
phorus or  less  is  present,  the  neutralization  must  be  closer  and  the 
time  allowed  for  precipitation  longer ;  with  pig  irons  abnormally 
high  in  phosphorus  (this  is  shown  by  the  quantity  of  the  yellow 
precipitate)  more  molybdate  should  be  added.  A  difficulty  often 
arises  when  the  ammoniacal  solution  of  the  yellow  precipitate  is 
acidified  —  the  precipitate  separates  out  again.  This  can  be  rem- 
edied by  more  sulphuric  acid,  or  better  by  redissolving  in  ammonia 
and  making  up  to  even  bulk  and  taking  an  aliquot  part  for  acidifi- 
cation and  titration.  This  will  avoid  the  reprecipitation  and  also 
using  perhaps  several  hundred  cubic  centimeters  of  permanganate. 

*  This  quantity  is  to  be  varied  so  as  to  obtain  a  solution  but  slightly  acid  as  is  shown 
by  the  color. 


50  QUANTITATIVE   ANALYSIS. 

The  solution  as  it  comes  from  the  reductor  should  be  olive 
green,  the  depth  of  color  depending  on  the  quantity  of  molyb- 
denum. On  adding  permanganate  different  colors  are  formed  as 
the  oxidation  progresses  until  finally  the  solution  becomes  color- 
less. It  is  a  pink  after  this  point,  which  marks  the  complete  re- 
oxidation  to  MoO3  and  is  taken  as  the  end  point. 

There  has  been  much  discussion  as  to  the  degree  of  reduction  of 
the  molybdenum  after  passing  through  the  reductor.  Under  the 
conditions  which  follow,  the  reduction  corresponds  to  an  oxide 
Mo,40jr 

There  is  no  evidence  of  the  existence  of  such  an  oxide,  nor  is 
there  a  definite  stopping  point  corresponding  to  this  degree  of  re- 
duction, but  under  certain  conditions  the  reduction  proceeds  to 
this  point,  viz.  :  Length  of  column  of  20-30  mesh  zinc,  37  cm. ; 
time  of  passage,  about  six  minutes;  temperature,  7O°-75°  C.; 
volume,  200  c.c.  ;  acidity,  10  c.c.  of  concentrated  sulphuric  acid. 
The  factor  for  converting  the  iron  standard  of  the  permanganate 
to  the  phosphorus  standard,  based  on  reduction  to  Mo24O3t  is 
0.01584;  while  the  factors  as  determined  experimentally*  are 
0.01579  for  unamalgamated  and  0.01586  for  amalgamated  zinc. 

The  factor  0.01538  corresponds  to  a  complete  reduction  to 
Mo2O3  and  should  be  used  when  the  molybdenum  is  reduced  as 
follows :  Dissolve  the  yellow  precipitate  in  ammonia  and  allow  it 
to  run  back  into  the  precipitation  flask  to  dissolve  what  adheres  to 
the  sides ;  the  volume  is  now  about  75  c.c. ;  add  5  grams  of  pulver- 
ized zinc,  100  mesh,  and  15  c.c.  of  cone,  sulphuric  acid.  Close  the 
flask  with  a  rubber  stopper  provided  with  a  bent  tube  dipping  into 
a  saturated  solution  of  sodium  bicarbonate  (compare  solution  of 
iron  wire).  Allow  to  stand  for  half  an  hour,  then  if  all  action  is 
over  and  the  temperature  is  about  40°  C.  it  is  ready  for  titration 
by  permanganate.  A  blank  must  be  run  on  another  portion  of  5 
grams  of  the  same  zinc  with  the  same  amounts  of  ammonia  and 
sulphuric  acid  and  the  amounts  of  permanganate  consumed  by  the 
iron  present  deducted  from  each  determination  made. 

CARBON  DETERMINATIONS. 

Steel  contains  carbon  combined  with  iron,  forming  different  car- 
bides of  which  cementite,  Fe3C,  is  one  of  the  most  important.  Cast 
iron,  in  addition  to  these,  contains  graphitic  carbon .  When  cast  iron 

*  Miller  and  Frank,/.  Am.  Chem.  Soc.,  Vol.  XXV.,  p.  925,  1903. 


PIG   IRON   AND    STEEL   ANALYSIS.  51 

or  steel  is  treated  with  strong  acid  the  combined  carbon  is  liberated 
as  a  hydrocarbon,  which  is  volatile,  and  so  a  portion  is  lost. 

When  the  total  carbon  is  to  be  determined  proceed  as  follows : 
Weigh  out  i  gram  of  pig-iron  ;  place  in  a  No.  2  beaker;  add  100  c.c. 
of  a  solution  of  copper  potassium  chloride  (containing  300  grams 
per  liter)  and  7.5  c.c.  of  concentrated  hydrochloric  acid.  For  steel, 
take  3  grams,  200  c.c.  of  the  double  chloride  solution  and  15  c.c.  of 
concentrated  hydrochloric  acid.  Stir  the  solution  at  the  ordinary 
temperature  until  the  iron  is  dissolved,  then  heat  to  about  60°  C.  and 
stir  till  the  precipitated  copper  has  gone  into  solution;  allow  to  settle 
and  filter  through  ignited  asbestos  in  a  small  funnel  or  perforated 
platinum  boat;  wash  with  hot  water,  dry,  and  burn  the  carbon  to 
carbon  dioxide  in  a  combustion  furnace  with  oxygen,  or  in  a  flask 
by  chromic  and  sulphuric  acids;  absorb  the  carbon  dioxide  in 
either  potassium  or  barium  hydroxide  solution  or  by  soda  lime,  and 
from  the  increased  weight  calculate  the  total  carbon. 

For  details  see  Blair  and  Cairns'  Quantitative  Analysis. 

The  reactions  which  take  place  are 

Fe  +  CuCl2  =  FeCl2  +  Cu. 
Fe3C  +  3CuCl2  =  3FeCl2  +  3Cu  +  C. 

Cu  +  CuCl2  =  2CuCl. 

The  potassium  chloride,  giving  double  salts,  only  hastens  the  solu- 
tion. 

When  the  hydrochloric  acid  exceeds  20  per  cent,  there  is  loss  oi 
combined  carbon. 

Graphite  is  most  accurately  determined  by  dissolving  3—5  grams 
of  pig  iron  in  nitric  acid  1.2  sp.  gr.,  using  15  c.c.  for  each  gram 
taken,  filtering  through  ignited  asbestos,  and  then  washing  with 
hot  water,  hot  potassium  hydroxide  solution,  i.i  sp.  gr.,hot  water, 
dilute  hydrochloric  acid,  alcohol,  ether  and  finally  with  hot  water  ; 
then  burning  to  carbon  dioxide. 

These  solutions  are  used  to  remove  iron  salts,  silica,  hydro- 
carbons, and  the  final  washing  with  water  is  to  remove  alcohol. 

This  method  is  long  and  for  rapid  work  and  approximate  re- 
sults the  following  may  be  used.  Crobaugh's  *  method  modified. 
Weigh  2-3  grams  of  drillings  and  transfer  them  to  a  125  c.c. 
platinum  dish,  add  100  c.c.  of  nitric  acid  1.135  SP-  gr-  and  warm 
to  hasten  solution  then  add  about  8  c.c.  of  40  per  cent,  hydrofluoric 

*/.  Am.  Chem.  Soc.,  Vol.  XVI.,  p.  104. 


52  QUANTITATIVE   ANALYSIS. 

acid  (B.  &  A.)  and  heat  for  ten  minutes.  Filter  at  once  on  balanced 
filters,  wash  with  water  four  times,  then  twice  with  hydrochloric 
acid  I :  I  or  till  all  iron  is  removed ;  then  with  ammonia  0.96  sp.  gr. 
until  the  washings  are  colorless,  to  remove  hydrocarbons,  then 
again  with  hydrochloric  acid  and  finally  with  water.  Separate 
the  two  papers  and  dry  them  at  ioo°-io5°  C,  place  one  on  each 
pan  of  the  balance  and  weigh  the  graphite.  Then  as  a  precaution 
burn  them  and  the  graphite  in  a  weighed  platinum  crucible  and 
deduct  any  residue  found  from  the  weight  of  graphite.  Also 
examine  this  residue  to  see  whether  any  iron  compound  has 
resisted  solution. 

Balanced  papers  are  obtained  by  taking  two  from  the  same 
package,  which  have  been  adjacent  and  so  presumably  contain  the 
same  amount  of  moisture,  and  placing  on  the  two  pans  of  the 
balance,  to  determine  which  is  the  heavier,  then  cutting  narrow 
strips  off  the  edges  of  the  heavier  till  they  balance.  They  are 
then  folded  and  placed  one  inside  the  other  and  the  original  solu- 
tion, as  well  as  all  washing  solutions  passed  through  both.  The 
assumption  is  made  that  as  they  weighed  the  same  in  the  begin- 
ning and  have  been  treated  in  the  same  way  throughout,  when 
dried  at  the  same  temperature  they  ought  still  to  weigh  the  same. 

Combined  carbon  in  steel  is  most  rapidly  determined  by  a  color 
comparison  as  follows : 

Weigh  out  0.2  gram  of  the  sample  and  0.2  gram  of  a  standard 
steel  in  which  the  carbon  has  been  accurately  determined  by  the 
combustion  method,  and  which  is  made  by  the  same  process  and 
is  in  the  same  physical  condition,  into  test-tubes  15  cm.  long;  add 
slowly  the  proper  amount  of  nitric  acid  1.2  sp.  gr. ;  for  steels  con- 
taining less  than  0.3  per  cent,  carbon  use  3c.c.;  O3.-O.5  per  cent. 
4  c.c.  ;  0.5-0.8  per  cent.  5  c.c.,  and  so  on ;  place  on  the  top  of  each 
test-tube  a  small  glass  funnel  or  marble,  put  the  tubes  in  a  water- 
bath  and  heat  to  boiling,  then  boil  till  all  carbonaceous  material 
has  dissolved,  shaking  occasionally.  This  requires  20  to  45  min- 
utes. Pour  into  graduated  tubes  and  dilute  one  or  the  other  till 
the  colors  match.  For  example,  if  the  standard  steel  contained  0.4 
per  cent,  carbon  and  when  diluted  to  8  c.c.  matched  the  other  steel 
when  diluted  to  1 3  c.c., —  the  sample  contains  0.65  per  cent,  carbon. 

The  entire  method  depends  on  having  two  steels  which  are 
almost  exactly  identical  and  then  treating  them  exactly  alike 
throughout.  Reverse  the  position  of  the  two  tubes  when  they 


PIG    IRON   AND    STEEL   ANALYSIS.  53 

appear  to  match  to  see  whether  they  still  agree  in  color  and  so 
offset  any  peculiarities  in  eyesight. 

SULPHUR  DETERMINATION. 
Sulphur  may  exist  in  four  different  forms  in  pig  iron : 

1.  That  evolved  as  hydrogen  sulphide  on  treatment  with  hydro- 
chloric acid. 

2.  That  which  is  evolved  as  an  organic  sulphide  (CH3)2S,  etc.; 
which  is  neither  absorbed  by  alkaline  solutions  nor  oxidized  by 
bromine  to  sulphate.     It  can  be  decomposed  by  passing  through 
a  red-hot  tube  mixed  with  carbon  dioxide  and  then  yields  hydro- 
gen sulphide. 

3.  That  which  is  not  attacked  by  hydrochloric  acid  but  is  oxi- 
dized by  nitric  acid  or  aqua  regia ;  perhaps  arsenic  and  titanium 
sulphides. 

4.  That  which  is  unacted  on  by  aqua  regia  and  requires  a  fusion 
to  obtain  it  in  solution. 

The  methods  for  determining  sulphur  are  usually  classed  as 
evolution  or  oxidation. 

The  evolution  methods  only  get  the  sulphur  in  (i)  but  if  all  the 
sulphur  is  present  in  this  condition  they  are  accurate.  The 
amount  of  sulphur  in  (2)  is  exceedingly  small  and  is  probably  lost 
by  any  method  in  use. 

The  oxidation  methods  get  (I )  and  (3)  and  if  the  residue  is  fused 
(I),  (3)  and  (4). 

It  has  been  shown  by  repeated  comparisons  that  the  evolution 
methods  are  unreliable  in  general  and  can  only  be  used  on  such 
material  as  is  known  to  give  up  its  sulphur  by  treatment  with 
hydrochloric  acid,  i.  e.,  steel  and  pig  iron  from  certain  ores. 

OXIDATION  METHODS. 

Method  of  Noyes  and  Helmer* — Put  200  c.c.  of  water  and  8  c.c. 
of  bromine  (free  from  sulphur)  in  a  flask  and  add  5  grams  of  iron 
or  steel  drillings  in  portions,  cooling  after  each  addition.  Solution 
takes  place  readily,  giving  ferric  bromide  and  sulphate.  When  it 
is  complete  boil  to  expel  the  slight  excess  of  bromine,  filter,  and 
wash  the  residue,  set  aside  the  filtrate.  To  the  residue  add  about 
2  grams  of  sodium  carbonate  and  burn  the  filter  in  a  platinum 
crucible,  using  an  alcohol  lamp  and  completing  the  oxidation  by 

*J.  Am.  C.  S.,  23,  675,  1901. 


54  QUANTITATIVE   ANALYSIS. 

the  addition  of  a  few  crystals  of  potassium  nitrate  and  reigniting. 
Dissolve  the  residue  in  water,  filter,  acidify  the  filtrate  with  hydro- 
chloric acid,  add  5  c.c.  of  barium  chloride  solution,  heat,  etc.,  and 
weigh  the  barium  sulphate  ;  add  three  fifths  of  the  weight  of  barium 
sulphate  found  here  to  that  obtained  from  the  filtrate.  Place  1 30 
c.c.  of  10  per  cent,  ammonia  into  a  5OO-c.c.  flask  and  pour  in  the 
filtrate,  dilute  to  the  mark  and  mix  thoroughly  by  pouring  into  a 
dry  beaker  and  back ;  filter  through  a  dry  filter.  Take  300  c.c. 
(three  fifths)  of  the  strongly  alkaline  filtrate  and  evaporate  it  in  a 
wide  beaker  to  about  100  c.c.,  taking  care  that  it  shall  not  absorb 
sulphur  from  the  gas.  Then  add  five  to  six  drops  of  dilute  hydro- 
chloric acid  and  precipitate  the  sulphur  as  barium  sulphate  in  the 
usual  manner.  To  the  barium  sulphate  so  obtained  three  fifths  of 
that  from  the  residue  and  calculate  the  results  on  three  grams  of 
steel. 

Notes.  —  This  method  is  both  accurate  and  rapid.  It  obtains  all 
but  the  organic  sulphide  which  may  be  present.  It  overcomes  the 
difficulty  of  washing  out  the  sulphate  from  the  bulky  ferric  hydrox- 
ide from  five  grams  of  iron,  by  taking  an  aliquot  part,  and  the 
many  troubles  which  arise  when  the  attempt  is  made  to  precipitate 
barium  sulphate  in  the  presence  of  iron. 

In  some  cases  more  than  eight  grams  of  bromine  are  required  to 
effect  complete  solution.  The  iron  should  be  added  slowly  and  in 
portions,  so  as  not  to  heat  the  solution  by  a  violent  reaction  and 
so  cause  a  separation  ot  a  basic  ferric  salt,  which  is  redissolved  with 
difficulty. 

The  only  possible  objections  to  this  method  are,  the  error  due  to 
the  volume  of  the  precipitate  when  an  aliquot  part  of  the  filtrate  is 
removed,  which  is  practically  nothing  with  material  so  low  in  sul- 
phur, and  the  possibility  of  contamination  of  the  barium  sulphate 
from  the  residue  by  hydrated  silica. 

BambeSs  Method  is  equally  accurate,  but  less  convenient.  Dis- 
solve at  least  5  grams  of  the  sample  in  strong  nitric  acid ;  add  2—5 
grams  of  potassium  nitrate ;  evaporate  to  dryness  in  a  platinum 
dish  and  ignite.  Boil  with  water  and  sodium  carbonate,  filter  and 
wash  with  water  containing  sodium  carbonate.  Acidulate  the  fil- 
trate with  hydrochloric  acid,  evaporate  to  dryness  to  dehydrate  the 
silica,  redissolve  in  water  and  a  few  drops  of  hydrochloric  acid, 
filter  and  determine  as  barium  sulphate.  For  further  details  see 
Blair  or  Jour.  Iron  and  Steel  Inst.,  1894,  p.  319. 


PIG    IRON   AND    STEEL   ANALYSIS.  55 

Sulphur  is  also  determined  *  by  the  precipitation  as  barium  sul- 
phate in  the  presence  of  iron,  but  the  method  is  open  to  serious 
objections.  On  account  of  the  solubility  of  barium  sulphate  in  hot 
acid  solutions  containing  ferric  chloride  the  precipitation  must  be 
made  in  a  solution  only  warm  and  then  must  be  allowed  to  cool 
before  filtration.  Under  these  conditions  the  precipitate  is  not 
only  difficult  to  filter,  but  is  usually  contaminated  by  iron.  The 
cause  of  the  contamination  as  given  by  Kuster  and  Thiel  f  is  the 
formation  of  the  insoluble  barium  salt  of  a  complex  ferrisulphuric 
acid,  Ba(Fe2S2O8)2,  which  loses  SO3on  ignition,  so  the  contaminated 
barium  sulphate  may  give  too  low,  not  too  high  results,  and  the 
purification  of  the  precipitate  only  increase  the  inaccuracy.  This 
trouble  can  be  avoided  by  precipitation  in  the  cold  or  by  pouring 
the  ferric  solution  into  the  barium  chloride,  but  it  is  preferable  to 
remove  the  iron  as  given  in  the  methods  described, 

EVOLUTION   METHOD.     CAMP'SJ  DESCRIPTION  OF  THE  ELLIOTT 

METHOD. 

Solutions  Required. 

Iodine.  —  Weigh  into  a  flask  about  18  grams  of  potassium  iodide 
and  8  grams  of  iodine  ;  add  water  and  shake  till  solution  is  com- 
plete, then  dilute  to  about  1.75  liters.  This  is  standardized  by 
steels  containing  known  amounts  of  sulphur. 

Cadmium  Chloride.  —  Dissolve  \2  grams  of  cadmium  chloride  in 
about  125  c.c.  of  water,  add  65  c.c.  of  strong  ammonia  and  filter 
into  a  liter  bottle ;  250  c.c.  of  water  are  added  and  the  solution 
made  up  to  a  liter  with  strong  ammonia. 

Starch  Solution.  —  Add  to  half  a  liter  of  boiling  water  in  a  liter 
flask,  3-4  grams  of  pure  starch,  previously  stirred  to  a  thin  paste 
with  cold  water  ;  this  is  boiled  for  ten  minutes  and,  when  cold,  3—4 
grams  of  pure  zinc  chloride  are  added  and  the  solution  diluted  to 
a  liter  with  cold  water.  The  clear  solution  is  siphoned  off  for  use 
and  keeps  well. 

Method.  —  Five  grams  of  pig  iron  or  steel  are  weighed  off  into  a 
dry  half-liter  flask,  provided  with  a  two-hole  rubber  stopper,  with 
funnel  tube  and  delivery  tube  with  a  rubber-tube  connection, 
which  is  connected  with  a  glass  tube  which  reaches  to  the  bottom 
of  a  test-tube  2.5  cm.  wide  and  25  cm.  deep.  In  this  is  placed  10 

*  Colby's  method  is  given  in  Cairns,  p.  170. 
f  Zeits.  fur  anorganische  Chemie,  XXII.,  424. 
J  Phillips'  "  Methods  of  Iron  Analysis,"  p.  41. 


56  QUANTITATIVE   ANALYSIS. 

c.c.  of  the  ammoniacal  cadmium  solution,  diluted  with  water  so 
that  it  fills  two  thirds  of  the  test-tube.  80  c.c.  of  hydrochloric 
acid  I  :  2  (1.07  sp.  gr.)  are  now  poured  into  the  flask  through  the 
funnel  tube  and  a  gentle  heat  applied  till  all  the  iron  has  dissolved, 
then  heated  to  boiling  until  nothing  but  steam  escapes.  The  ap- 
paratus is  then  disconnected  and  the  delivery  tube  placed  in  a  No. 
4  beaker,  and  the  contents  of  the  test-tube  poured  in,  then  the  test- 
tube  is  rinsed  out  with  25  c.c.  of  dilute  hydrochloric  acid  and  with 
water  and  the  rinsings  added  to  the  beaker.  The  volume  of  the 
solution  should  be  about  400  c.c.,  when  the  cadmium  sulphide  has 
dissolved,  .5  c.c.  of  starch  solution  are  added  and  the  standard 
iodine  run  in  till  a  permanent  blue  color  is  obtained.  The  iodine 
can  be  adjusted  to  read  one  hundredth  of  a  per  cent,  of  sulphur 
for  each  cubic  centimeter  when  5  grams  are  taken  for  analysis. 

The  chemistry  of  the  process  is  as  follows :  The  sulphur  is  liber- 
ated as  hydrogen  sulphide;  this  is  absorbed  by  the  ammoniacal 
cadmium  solution,  giving  yellow  cadmium  sulphide,  which  is  easily 
dissolved  in  dilute  hydrochloric  acid,  giving  hydrogen  sulphide 
again  which  remains  dissolved  in  the  large  volume  of  water  pres- 
ent, 400  c.c.  The  iodine  solution  reacts  H2S  -f  I2  =  2HI  -f  S,  in  a 
dilute  solution.  Then  the  least  excess  of  iodine  gives  an  intense 
blue  with  starch  which  is  the  end  point. 

SILICON   DETERMINATION. 

Brown's  method  or  some  modification  is  always  used.  Treat 
one  gram  of  borings  with  20  c.c.  of  nitric  acid  1.2  sp.  gr.  in  a  plati- 
num or  porcelain  dish  or  casserole.  When  all  action  has  ceased 
add  20  c.c.  of  sulphuric  acid  i  :  I  and  evaporate  to  copious  fumes 
of  sulphuric  anhydride,  allow  to  cool  and  dilute  carefully  with 
150  c.c.  of  water,  heat  to  dissolve  ferric  sulphate,  filter  hot  and 
wash  first  with  hydrochloric  acid  I  :  I  and  then  with  water  till  free 
from  iron.  Burn  off  the  carbon  in  a  weighed  platinum  crucible 
and  weigh  the  SiO2 ;  check  by  driving  it  off  with  hydrofluoric  acid. 

Notes. —  Nitric  acid  should  be  used,  not  hydrochloric,  as  there 
may  be  a  titanium  carbide  present  which  is  not  attacked  by  hy- 
drochloric acid  alone.  Modifications  are  to  add  both  acids  at 
once  i.  e.,  nitro-sulphuric  acid.  This  is  made  by  adding  60  c.c.  of 
cone,  sulphuric  acid  to  600  c.c.  nitric  acid  1.2  sp.  gr.  30  c.c.  are 
used  for  each  gram  of  drillings. 


PIG    IRON   AND    STEEL   ANALYSIS.  S7 

The  sulphuric  acid  takes  the  water  from  the  silica  and  so  renders 
it  insoluble.  This  method  is  more  rapid  than  dehydration  by 
means  of  heat  alone  but  is  limited  in  its  application  to  those  cases 
where  insoluble  sulphates  are  not  present.  Like  the  method 
described  under  iron  ore,  traces  of  silica  escape  when  only  one 
evaporation  is  made,  but  the  quantity  present  is  so  small  that  a 
second  dehydration  is  rarely  necessary. 

DETERMINATION  OF  MANGANESE. 

Manganese  in  steel  is  usually  determined  colorimetrically  after 
oxidation  to  permanganic  acid  by  lead  peroxide  in  a  nitric  acid 
solution,  but  the  method  proposed  by  Walters  *  seems  preferable. 
Weigh  0.2  gram  of  the  steel  to  be  tested  and  the  same  quantity  of 
a  standard  steel  of  known  manganese  content  into  two  large  test- 
tubes.  Add  10  c.c.  nitric  acid  1.2  sp.  gr.  to  each  and  heat  them 
in  a  water-bath  till  the  nitrous  fumes  are  driven  off.  Next  add  15 
c.c.  of  a  solution  of  silver  nitrate  containing  1.33  grams  to  the 
liter,  and  then  immediately  about  a  gram  of  moist  ammonium  per- 
sulphate, (NH4)2S2O8,  to  each ;  continue  heating  till  the  oxidation 
is  complete,  then  half  a  minute  longer.  Remove  the  tubes,  while 
the  oxygen  continues  to  come  off,  and  place  them  in  cold  water. 
When  cool  compare  the  colors  as  described  under  combined  carbon. 

Notes. —  When  the  manganese  is  over  0.75  per  cent,  use  only 
o.i  gram  of  steel.  The  ammonium  persulphate  loses  its  efficiency 
unless  it  is  kept  moist.  The  method  can  be  applied  to  pig  iron 
by  filtering  off  the  carbon,  etc.,  or  can  be  changed  to  a  volumetric 
method  by  titrating  the  permanganate  by  a  standard  arsenite 
solution  as  described  by  Stehman  in  the  Journal  of  the  American 
Chemical  Society  for  December,  1902. 

ADDITIONAL  REFERENCES. 
BLAIR.     The  Chemical  Analysis  of  Iron. 
PHILLIPS.     Methods  of  Iron  Analysis. 
LORD.     Notes  on  Metallurgical  Analysis. 
ARNOLD.     Steel  Works  Analysis. 

BREARLEY  AND  IBBOTSON.     The  Analysis  of  Steel  Works  Materials. 
DROWN.     Influence  of  Silicon  on  the  Determination  of  Phosphorus 

in  Iron.     Trans.  Am.  I.  M.  E.,  June,  1889. 
THACKRAY.     A  Comparison  of  Recent  Phosphorus  Determinations 

in  Steel.     Trans.  Am.  I.  M.  E.,  October,  1895. 

*  Walters,  Chemical  News,  Nov.  15,  1901. 


58  QUANTITATIVE   ANALYSIS. 

SHIMER.     Carbon  Combustions  in  a  Platinum  Crucible.     J.  Am. 

Chem.  Soc.,  July,  1899. 
DUDLEY  AND  PEASE.     Need  of  Standard  Methods,    etc.     J.  Am. 

Chem.  Soc.,  September,  1893. 
LINDSAY.      Colorimetric    Method  for  Sulphur  in    Pig   Iron,    etc. 

School  of  Mines  Quarterly,  Vol.  23,  p.  24. 
SARGENT.     Use  of  Potassium  Ferric  Chloride  for  the  Solution  of 

Steel  in  making  the  Determination  of  Carbon.     J.  Am.  Chem. 

Soc.,  24,  1076,  1902. 
GLADDING.    Gravimetric  Method  of  Estimating  Phosphoric  Acid  as 

Ammonium  Phospho-molybdate.     J.  Am.  Chem.  Soc.,  18,  23. 
KILGORE.     Titration  of  Ammonium  Phospho-molybdate  by  Stan- 
dard Alkali.     J.  Am.  Chem.  Soc.,  19,  703. 
SHERMAN  AND  HYDE.     On  the  Determination  of  Phosphoric  Acid  as 

Phospho-molybdic  Anhydride.     J.  Am.  Chem.  Soc.,  22,  652. 


DETERMINATION    OF   MANGANESE.  59 


CHAPTER  VIII. 

Determination  of  Manganese  in  Spiegel  and  in 
Manganese  Ores. 

VOLHARD'S  METHOD. 

This  is  based  on  the  following  reaction  which  takes  place  in  a 
hot  dilute  neutral  solution  containing  zinc  sulphate  or  nitrate,  in 
which  the  manganese  is  present  as  sulphate  or  as  nitrate  : 

3MnSO4  +  2KMnO4  +  2H2O  =  5MnO2  +  K2SO4+  2H2SO4. 
The  neutrality  is  maintained  by  the  excess  of  zinc  oxide  present. 
Many  modifications  of  the  original  method  have  been  proposed, 
neutralizing  with  barium  carbonate,  sodium  bicarbonate,  etc.,  but 
the  only  change  which  is  an  improvement  is  Stone's  use  of  nitric 
acid  in  the  case  of  spiegels. 

The  tenth  normal  permanganate  solution  may  be  used  again  here 
or  if  one  is  to  be  made  up  especially,  2  grams  per  liter  is  a  con- 
venient strength.  The  manganese  standard  can  be  calculated  from 
the  iron  standard,  but  it  is  preferable  to  standardize  against  aspiegel 
of  known  manganese  content. 

Manganese  Ore.  —  Treat  one  gram  of  the  manganese  ore,  ground 
extremely  fine,  in  a  casserole  with  10  c.c.  of  concentrated  hydro- 
chloric acid  and  if  necessary  a  little  nitric  acid  to  ensure  the  oxida- 
tion of  the  iron  present.  When  pyrolusite,  etc.,  are  to  be  analyzed 
of  course  the  nitric  acid  is  unnecessary ;  heat  till  complete  decompo- 
sition is  effected,  then  add  25  c.c.  of  water  and  5  c.c.  of  concen- 
trated sulphuric  acid  and  evaporate  to  fumes  of  sulphuric  anhy- 
dride;  cool,  dilute  to  about  150  c.c.  and  heat  to  dissolve  the 
sulphates  completely.  Examine  the  insoluble  residue  to  see 
whether  it  is  completely  decomposed ;  if  not,  as  would  be  the  case 
with  franklinite,  filter;  fuse  the  residue  with  mixed  carbonates, 
dissolve  in  hydrchloric  acid,  evaporate  to  fumes  with  sulphuric 
acid  and  add  the  solution,  after  diluting,  to  the  main  portion. 

Nearly  neutralize  the  sulphate  solution  with  a  saturated  solution 
of  crystallized  sodium  carbonate,  transfer  to  a  liter  flask  and  add  a 
cream  of  zinc  oxide  (free  from  manganese)  until  the  precipitate  of 
ferric  hydroxide,  etc.,  settles  rapidly ;  shake  after  each  addition  of 
zinc  oxide,  so  as  not  to  use  an  unnecessary  excess.  Allow  the 


60  QUANTITATIVE   ANALYSIS. 

solution  to  cool  and  dilute  to  the  mark.  Mix  thoroughly  by 
pouring  into  a  large  beaker  and  back  into  the  flask;  it  makes  no 
difference  whether  any  is  lost  after  mixing,  as  only  portions  are 
taken  for  titration.  Either  filter  through  a  dry  paper  and  take  out 
portions  of  either  100  or  200  c.c.  each,  depending  on  the  richness 
of  the  ore,  or  withdraw  such  portions  by  a  pipette  from  the  cloudy 
liquid  above  the  brownish  precipitate  in  the  flask. 

Place  the  portions  in  small  casseroles  and  if  looc.c.  is  taken  di- 
lute it  to  about  200  c.c.  with  water.  Heat  to  boiling,  and  while 
hot  run  in  permanganate  rapidly  I  c.c.  at  a  time,  stirring  vigorously 
with  a  bent  glass  rod  till  a  faint  pink  is  seen  against  the  side  of 
the  casserole  after  the  precipitated  manganese  dioxide  has  settled  ; 
then  stir  hard  again  to  make  sure  that  the  color  is  permanent,  for 
it  sometimes  stirs  out  and  then  more  permanganate  is  required. 
The  first  portion  is  run  rapidly  to  get  an  idea  of  the  amount  re- 
quired, the  others  quickly  up  to  within  I  c.c.  of  the  amount  used  on 
the  first  titration ;  then  carefully,  a  drop  at  a  time,  till  the  faint 
permanent  pink  color  is  obtained.  The  reason  for  this  is  that 
when  the  permanganate  is  run  in  slowly  the  dioxide  adheres  to 
the  sides  of  the  casserole,  so  that  there  is  no  longer  a  good  back- 
ground for  the  end  point,  and  also  because  the  solution  becomes 
cold,  which  renders  the  reaction  less  prompt.  Several  portions  can 
be  run  from  the  original  gram  till  satisfactory  duplicates  are  ob- 
tained. 

With  spiegel  the  method  can  be  made  even  shorter.  Dissolve 
one  gram  in  about  15  c.c.  of  nitric  acid,  1.2  sp.  gr. ;  boil  out  fumes, 
etc.,  neutralize  with  sodium  carbonate  solution,  and  proceed  as 
described. 

Notes. — The  original  Volhard  method  required  sulphates,  but 
it  has  been  shown  that  nitrates  are  permissible  but  chlorides  objec- 
tionable. As  manganese  dioxide  is  insoluble  in  nitric  acid  we  can- 
not use  this  acid  for  the  solution  of  all  manganese  minerals  and 
so  Volhard's  method  is  given  for  ores. 

Neutralizing  by  sodium  carbonate  is  carried  on  till  a  reddish 
color  is  produced  but  no  precipitate.  The  zinc  oxide  is  ground  up 
in  a  porcelain  mortar  with  water  and  the  creamy  liquid  poured  off 
for  use.  Lumps  of  zinc  oxide  are  of  no  use  and  by  occupying 
space  cause  an  inaccuracy  when  we  withdraw  say  one  fifth  of  the 
solution  and  consider  that  it  contains  the  manganese  from  one 
fifth  of  the  amount  taken.  Notwithstanding  the  error  introduced 


DETERMINATION    OF   MANGANESE.  61 

by  the  volume  of  the  precipitate  and  of  the  zinc  oxide  it  is  better 
not  to  allow  for  them  as  there  is  another  cause  of  error  which  this 
partly  compensates.  The  precipitate  formed  by  the  permanganate 
is  not  always  exactly  hydrated  MnO2 ;  it  may  be  very  slightly  defi- 
cient in  oxygen.  So  the  best  method  is  to  standardize  on  a  similar 
Spiegel  or  ore  in  which  the  manganese  has  been  determined  gravi- 
metrically  rather  than  to  calculate  from  the  iron  standard.  Barium 
carbonate  can  be  used  to  neutralize  but  the  end  point  is  not  as 
sharp  as  with  zinc  oxide.  There  has  been  much  discussion  as  to 
the  excess  of  zinc  oxide  and  the  manner  of  adding  it ;  probably  it 
is  best  to  add  but  a  slight  excess  in  order  to  precipitate  the  iron 
and  then  after  dilution  to  add  more.  It  is  however  important  to 
do  this  the  same  way  each  time  and  exactly  as  in  standardizing. 

CHLORATE  SEPARATION  (HAMPE). 

This  depends  on  the  fact  that  the  addition  of  crystals  of  potas- 
sium or  sodium  chlorate  to  a  solution  of  manganese  in  strong  nitric 
acid  precipitates  the  manganese  as  dioxide  on  boiling.  If  iron  is 
present  a  small  amount  precipitates  with  the  MnOa.  Chlorides 
must  be  absent  or  the  precipitation  is  incomplete. 

The  nitric  acid  solution  is  boiled  down  to  expel  other  acids,  etc. 
75  c.c.  of  concentrated  nitric  acid  are  added  and  the  solution 
heated,  then  3-4  grams  of  chlorate,  then  heated  to  boiling  for  ten 
minutes,  allowed  to  cool  somewhat  and  another  portion  of  chlorate 
is  added,  followed  by  another  boiling ;  after  cooling,  the  dioxide  is 
filtered  on  asbestos  and  washed  with  strong  nitric  acid,  then  with 
water.  The  oxidizing  power  of  the  precipitate  can  be  determined 
or  it  can  be  dissolved  and  the  manganese  determined  gravimetri- 
cally  after  the  removal  of  the  iron.  The  method  is  used  for  spiegel, 
etc.,  and  is  useful  for  separating  small  amounts  of  manganese  from 
large  quantities  of  iron  in  pig  iron,  etc.  See  Ford's  and  Williams' 
methods  in  Blair's  "  Chemical  Analysis  of  Iron." 

GRAVIMETRIC  METHOD  FOR  SPIEGEL. 

Dissolve  one  gram  of  the  finely  ground  sample,  for  spiegel  is 
brittle  and  can  be  pulverized  in  a  harveyized  steel  mortar,  in 
about  15  c.c.  of  nitric  acid,  1.2  sp.  gr.,  in  a  small  beaker,  evaporate 
to  dryness  and  bake  to  decompose  the  hydrocarbons  and  dehy- 
drate the  silica ;  add  20  c.c.  of  hydrochloric  acid  I  :  I  and  heat  till 
the  iron  is  all  dissolved ;  evaporate  nearly  to  dryness  to  expel  ni- 
tric acid  ;  take  up  with  water  and  hydrochloric  acid,  if  necessary 


62  QUANTITATIVE   ANALYSIS. 

to  give  a  clear  solution,  and  filter  out  the  residue  of  silica,  etc. 
We  now  have  the  iron <  as  ferric  chloride,  the  manganese  as  manga- 
nous  chloride  in  a  bulk  of  about  100  c.c.  slightly  acid  with  hy- 
drochloric acid  and  no  nitrates  present.  To  this  solution  add  a 
solution  of  crystallized  sodium  carbonate  till  a  very  slight  per- 
manent precipitate  is  formed  ;  dissolve  this  in  a  few  drops  of  dilute 
hydrochloric  acid.  Transfer  the  clear  deep  red  solution  to  a  large 
beaker  and  dilute  with  cold  water  to  about  700  c.c.;  the  solution 
should  remain  clear.  Add  one  gram  of  sodium  acetate  (3  c.c.  of  a 
saturated  solution),  heat  to  boiling  as  quickly  as  possible  and  boil 
for  three  minutes ;  slow  heating  or  long  boiling  gives  a  slimy  pre- 
cipitate which  is  hard  to  filter.  Filter  through  a  fluted  paper  and 
wash  with  boiling  water.  The  solution  must  be  filtered  hot,  as 
the  precipitate  is  likely  to  redissolve  in  the  acetic  acid  present  if 
allowed  to  cool.  Redissolve  the  precipitate  in  hot  dilute  hydro- 
chloric acid  and  repeat  the  "  basic  acetate  "  precipitation.  Com- 
bine the  filtrates  and  evaporate  them  to  about  350  c.c.;  if  any  iron 
separates,  filter,  dissolve  this  in  hydrochloric  acid  and  make  a  small 
basic  acetate  precipitation  to  recover  any  manganese  present ; 
combine  the  filtrates. 

NOTES  ON  THE  "  BASIC  ACETATE  "  SEPARATION. 

This  is  one  of  the  oldest  and  most  important  separations  in 
analytical  chemistry,  and  depends  on  the  hydrolytic  action  of  boil- 
ing water.  It  serves  for  the  separation  of  the  triad  elements,  iron, 
aluminum,  chrominum,  etc.,  from  the  dyad  elements  manganese, 
zinc,  cobalt,  nickel,  etc.  It  is  evident  therefore  that  all  the  iron 
must  be  in  the  ferric  condition  and  the  manganese  in  the  manga- 
nous,  for  ferrous  iron  is  not  precipitated  (dyad),  while  manganic  man- 
ganese is.  This  condition  is  readily  obtained  by  boiling  the  solu- 
tion after  oxidation  which  quickly  decomposes  the  unstable  higher 
chlorides  of  manganese.  The  separation  may  be  complete  from 
zinc  but  has  to  be  repeated  to  ensure  absence  of  manganese  from 
the  precipitate  which  is  likely  to  retain  nickel,  cobalt  or  copper 
even  after  several  reprecipitations. 

Ferric  iron  is  a  weak  base.  We  first  neutralize  nearly  all  of  the 
free  acid  (HC1),  then  add  sodium  acetate  which  forms  sodium 
chloride  and  free  acetic  acid ;  the  iron  is  also  largely  converted  to 
acetate,  as  is  shown  by  the  deep,  blood-red  color  which  is  formed 
at  this  point.  The  solution  is  now  ready  for  the  hydrolysis.  The 


DETERMINATION    OF   MANGANESE.  63 

rule  for  dilution  is  100  c.c.  for  every  o.i  gram  of  iron  present,  L  e., 
for  I  gram  of  Spiegel  700-800  c.c.  The  reagent  is  in  reality  boiling 
water,  which,  now  that  we  have  the  ferric  iron  combined  with  the 
weak  acid  (acetic),  reacts,  giving  a  basic  acetate  of  iron  and  free 
but  largely  undissociated  acetic  acid. 

The  composition  of  the  precipitate  is  not  uniform  as  the  replace- 
ment of  C2HSO2  groups  by  hydroxyl  goes  on  as  the  boiling  pro- 
gresses. It  may  be  Fe2(OH)2(C2H3O2)4,  Fe3(OH)3(C2H3O2) ,  etc.  If 
the  boiling  is  excessive  two  troubles  may  arise;  the  precipitate 
with  many  (OH)  groups,  approaching  the  hydroxide,  is  slimy  and 
the  acetic  acid  in  solution  may  reach  a  concentration  where  the 
reverse  reaction  takes  place  and  the  precipitate  dissolves.  This  is 
most  likely  to  result  if  the  solution  is  allowed  to  cool,  for  then  the 
hydrolytic  action  is  less  strong  and  the  reverse  action  has  a  chance 
to  progress  until  equilibrium  is  again  established,  and  we  find  iron 
in  the  filtrate.  The  filtrate  should  be  tested  for  iron  by  a  ferro- 
cyanide,  not  by  a  thiocyanate,  in  this  solution  containing  acetates. 

Fresenius  gives  the  dilution  already  mentioned  and  the  acidity 
about  one  per  cent,  of  absolute  acetic  acid.  If  too  little  acetic 
acid  is  present  the  hydrolytic  action  is  too  strong  and  manganese 
as  well  as  zinc,  nickel,  cobalt,  etc.,  come  down  with  the  iron, 
alumina,  etc.  Titanium,  if  present,  is  precipitated  with  the  iron, 
also  phosphorus,  arsenic  and  vanadium  in  combination,  as  when 
ammonia  is  used. 

By  bearing  in  mind  these  principles  it  is  easy  to  adapt  the 
method  to  a  manganese  ore.  Here  the  iron  is  low,  the  manganese 
higher.  The  chloride  solution  is  neutralized  in  small  volume,  the 
red  color  will  be  faint,  then  diluted  somewhat —  probably  200  c.c. 
will  be  sufficient  —  then  less  sodium  acetate  is  added,  about  half  a 
gram,  with  perhaps  a  little  acetic  acid. 

With  ferromanganese  the  procedure  is  similar,  for  the  manga- 
nese is  3-4  times  the  iron.  In  the  case  of  an  iron  ore,  when 
manganese  is  to  be  determined,  this  separation  is  substituted  for  the 
ammonia  precipitation,  then  the  manganese  is  taken  out  of  the 
filtrate  by  bromine  and  the  filtrate  used  for  lime  and  magnesia  as 
will  be  described  under  limestone. 

The  method  is  of  very  general  application,  but  must  be  adapted 
to  the  particular  analysis.  The  precipitate  is  never  ignited  and 
weighed,  on  account  of  the  alkaline  salts,  etc.,  if  the  oxides  and 
phosphates  of  iron,  aluminum,  etc.,  are  to  be  weighed  together  as 


64  QUANTITATIVE   ANALYSIS. 

in  an  iron  ore,  the  basic  acetate  precipitate  is  dissolved  in  hydro- 
chloric acid  and  reprecipitated  by  ammonia.  It  is  not  advisable 
to  determine  sulphur  in  the  filtrate  from  this  method  on  account 
of  the  likelihood  of  there  being  sulphur  in  the  reagents. 

The  description  of  the  gravimetric  determination  of  manganese 
is  taken  up  in  general  from  this  point. 

REMOVAL  OF  NICKEL  AND  COBALT. 

To  the  solution  in  a  casserole  add  ten  grams  of  sodium  acetate 
and  a  few  drops  of  acetic  acid  so  as  to  give  a  solution  but  faintly 
acid  with  acetic;  heat  to  boiling  and  pass  in  hydrogen  sulphide 
while  hot.  This  will  precipitate  the  sulphides  of  nickel,  cobalt  and 
copper  if  present,  and  manganese  ores  often  contain  cobalt  ;  when 
the  solution  is  saturated  with  hydrogen  sulphide,  digest  for  a  time 
hot,  then  filter,  and  wash  with  hydrogen  sulphide  water. 

Cobalt  and  nickel  are  often  present  and  must  be  removed  before 
we  throw  down  the  manganese  by  bromine,  for  they  also  give  black 
higher  hydroxides.  The  conditions  for  their  precipitation  as  sul- 
phide must  be  carefully  maintained. 

Manganous  sulphide  is  soluble  in  hydrochloric  and  acetic  acids  ; 
zinc  sulphide  is  soluble  in  hydrochloric  not  in  acetic  acid. 

Nickel  and  cobalt  sulphides,  when  once  formed  are  insoluble 
in  either  hydrochloric  or  acetic  acids,  but  are  prevented  from  pre- 
cipitating by  either  acid  in  the  cold  and  by  hydrochloric  or  much 
acetic  acid  when  hot.  However  when  hot  and  the  acetic  acid 
rendered  weak  by  the  mass  action  of  the  sodium  acetate,  nickel  and 
cobalt  sulphides  will  precipitate.  If  they  are  contaminated  by 
manganous  sulphide  this  can  easily  be  leached  out  by  washing 
with  hydrochloric  acid  1.025  sp.  gr.  saturated  by  hydrogen  sul- 
phide. 

The  explanation  of  the  strange  action  of  these  sulphides  is  that 
they  exist  in  two  modifications  —  a  soluble  and  an  insoluble —  and 
that  on  standing  or  on  heating  the  soluble,  which  forms  first,  is 
converted  into  the  insoluble,  which  then  requires  aqua  regia  for 
its  solution.* 

PRECIPITATION  OF  MANGANESE  BY  BROMINE. 
The  next  step  is  the  precipitation  of  the  manganese  by  bromine. 
This  might  seem  unnecessary  in  the  case  of  a  Spiegel  where  there 
are  no  salts  of  lime,  magnesia,  zinc,  etc.,  which  give  insoluble  phos- 

*Herz,  Z.  fur  Anorganische  Chemie,  28,  342,  1901. 


DETERMINATION    OF   MANGANESE.  65 

phates,  but  there  is  such  an  accumulation  of  sodium  salts,  etc.,  that 
a  reprecipitation  of  the  manganous  ammonium  phosphate  is  neces- 
sary, so  that  it  is  a  better  plan  to  throw  out  the  manganese  as 
dioxide.  Boil  out  the  sulphuretted  hydrogen  from  the  filtrate, 
allow  it  to  cool  and  add  2-3  c.c.  of  bromine  (not  bromine  water) ; 
heat  to  expel  the  excess  of  bromine  and  filter  ;  to  the  filtrate  add  a 
few  drops  of  bromine  and  a  little  sodium  carbonate  to  bring  the 
solution  nearly  to  the  neutral  point  and  heat  again  to  insure  com- 
plete precipitation  of  the  manganese. 

If  the  solution  is  too  acid  the  first  precipitation  may  not  be  com- 
plete ;  if  insufficiently  acid  some  manganese  may  be  oxidized  to 
permanganate.  When  this  happens  it  can  easily  be  reduced  by 
heating  with  a  few  drops  of  alcohol  or  of  sulphurous  acid. 

The  hydrated  manganese  dioxide  is  washed  with  hot  water,  and 
then  dissolved  in  a  little  hot  hydrochloric  acid  I  :  I  to  which  a  few 
c.c.  of  sulphurous  acid  have  been  added  to  cause  a  ready  solution 
of  the  dioxide  giving  manganous  chloride  (compare  addition  of 
stannous  chloride  in  iron  ores). 

Sometimes  in  evaporating  the  filtrate  from  the  basic  acetate 
precipitate  manganese  dioxide  separates  out.  If  this  is  free  from 
iron  it  can  be  filtered  and  added  to  the  rest. 

PRECIPITATION  OF  MANGANESE  AS  PHOSPHATE. 

There  can  be  no  doubt  that  of  all  the  methods  so  far  proposed 
for  the  determination  of  manganese  this  is  the  most  accurate  and 
satisfactory.  To  the  hydrochloric  acid  solution  add  a  decided  ex- 
cess, at  least  five  times  the  calculated  quantity  of  either  micro- 
cosmic  salt,  NaNH,HPO4,  dissolved  in  water  or  (NH4)2HPO4  solu- 
tion, which  is  readily  prepared  by  neutralizing  phosphoric  acid 
with  ammonia  till  it  just  turns  phenol-phthalein  pink ;  heat,  then 
add  ammonia  until  the  precipitate  forms  but  avoid  an  excess. 

The  first  precipitate  is  somewhat  flocculent  and  contains  Mn3- 
(PO4)2 ;  this  is  heated  on  the  water-bath  until  it  becomes  crystalline 
and  settles  almost  at  once  when  stirred.  The  MnNH4PO4.H2O 
so  formed  is  nearly  white  with  a  characteristic  nacreous  luster  and 
is  one  of  the  easiest  precipitates  known  to  filter  and  wash.  Allow 
the  solution  to  cool  and  filter  as  usual,  wash  with  water  or  better 
with  a  I  per  cent,  solution  of  the  precipitant,  followed  by  dilute 
alcohol ;  dry  separate  from  the  paper  ;  burn  the  paper,  moistened 
with  nitric  acid,  add  the  precipitate,  ignite  strongly  and  weigh  the 


66  QUANTITATIVE   ANALYSIS. 

manganous  pyrophosphate,  Mn2P2O7.  Or  else  filter  on  washed 
asbestos  (amphibole  not  serpentine)  in  a  Gooch  crucible  and  weigh 
after  drying  to  constant  weight  at  100-105°  C.,  as  MnNH4PO4 
H,0. 

Instead  of  asbestos,  balanced  or  weighed  filter  papers  may  be  used. 

Notes.  —  Before  applying  this  method  of  precipitation  the  man- 
ganese must  be  separated  from  all  metals  except  the  alkalies.  In 
forming  the  precipitate  there  must  be  a  sufficient  concentration  of 
NH4  ions  to  change  the  Mn3PO4  formed  at  first  to  the  MnNH4PO4; 
this  is  supplied  by  the  great  excess  of  (NHJ2HPO4  or  by  the 
precipitant  and  NH4C1  when  microcosmic  salt  is  used.  Serpen- 
tine asbestos  is  soluble  in  the  phosphate  solutions  and  must  not  be 
used. 

An  excess  of  ammonia  turns  the  precipitate  brown.  If  this 
happens,  dissolve  in  hydrochloric  acid  and  reprecipitate. 

It  is  best  to  separate  this  precipitate  from  the  paper  as  it  oc- 
casionally becomes  reduced,  giving  a  phosphide  which  damages 
the  platinum. 

ADDITIONAL  REFERENCES. 

BREARLEY.   Estimation  of  Manganese  in  Spiegels.  Chemical  News, 

75,  13- 
KNORRE.     Ueber  eine  neue  Methode  zur  Manganbestimmung.     Z. 

fiir  Angewandte  Chemie,  14,  1149. 
HILDRETH.     On   the   Determination   of    Manganese   in   Spiegel. 

School  of  Mines  Quarterly,  23,  27. 


DETERMINATION    OF   ZINC  IN   ORES.  67 


CHAPTER  IX. 

Determination  of  Zinc  in  Ores. 

VOLUMETRIC  METHOD  BY  POTASSIUM  FERROCYANIDE. 

Zinc  is  precipitated  by  potassium  ferrocyanide  in  a  solution, 
acid  with  hydrochloric,  according  to  the  reaction :  3ZnCl2  + 
2K4Fe(CN)6  =  ZnsK2Fe2(CN)12  +  6KC1.  The  end  point  is  shown 
by  the  formation  of  a  brown  color  when  a  drop  of  the  solution  is 
placed  in  contact  with  a  drop  of  a  uranium  solution,  preferably  the 
nitrate.  The  brown  is  caused  by  the  formation  of  uranium  ferro- 
cyanide by  the  slight  excess  of  potassium  ferrocyanide.  The 
method  when  properly  carried  out  is  rapid  and  yields  very  satis- 
factory results ;  anything  which  decomposes  or  oxidizes  the  ferro- 
cyanide must  be  absent,  /.  e.,  strong  acids,  chlorine,  etc.,  and  also 
all  of  the  numerous  metals  which  give  insoluble  or  sparingly  sol- 
uble ferrocyanides.  Those  most  likely  to  be  present  in  zinc  ores 
are  cadmium,  copper,  iron,  manganese,  nickel,  cobalt,  antimony  and 
aluminum. 

Solutions.  —  A  standard  solution  of  potassium  ferrocyanide,  made 
by  dissolving  43.2  grams  of  the  crystallized  salt,  K4Fe(CN)$.3H2O, 
in  cold  water  and  diluting  to  two  liters.  One  c.c.  will  be  equiva- 
lent to  about  5  milligrams  of  zinc ;  a  5  percent,  solution  of  uranium 
nitrate;  a  solution  of  ammonium  chloride,  10  grams  per  liter. 

Standardizing.  —  As  the  end  point  is  not  very  sensitive,  in  the 
presence  of  hydrochloric  acid,  it  is  necessary  to  deduct  from  each 
reading  the  amount  of  the  solution  in  excess  necessary  to  give  a 
certain  color  with  the  uranium  nitrate.  Further,  as  uranium  ferro- 
cyanide is  soluble  in  hydrochloric  acid,  the  excess  required  for  a 
definite  color  is  dependent  on  the  acidity  of  the  solution.  Also 
the  composition  of  the  precipitate  varies,  depending  whether  the 
solution  is  alkaline  (NH^H)  neutral,  acid  with  acetic  or  acid  with 
hydrochloric ;  and  if  the  excess  of  hydrochloric  acid  is  too  great, 
10  c.c.  of  concentrated  or  more,  and  the  solution  titrated  nearly 
boiling,  there  is  likely  to  result  a  decomposition  with  the  forma- 
tion of  blue  precipitates  or  colors,  which  spoil  the  determination. 


68  QUANTITATIVE   ANALYSIS. 

These  considerations  make  it  imperative  to  decide  at  once  the 
exact  conditions  for  titration,  and  then  to  determine  the  allowance 
for  the  indicator  under  exactly  these  conditions. 

The  following  are  of  the  most  general  application :  volume, 
200  c.c. ;  acidity ,  6  c.c.  of  concentrated  hydrochloric  acid ;  tempera- 
ture, 70°  C.  (about);  ammonium  chloride  present  about  10  grams. 
The  ammonium  chloride  is  added  as  it  affects  the  appearance  of 
the  precipitate  somewhat  and  is  usually  present  when  the  titration 
is  made.  It  seems  to  sharpen  the  end  point  slightly.  These  con- 
ditions allow  for  the  presence  of  lead,  which  is  likely  to  be  present 
from  the  ore  or  from  the  test  lead  used  to  remove  copper,  as  6  c.c. 
of  hydrochloric  acid  in  200  c.c.  completely  prevent  the  precipi- 
tation of  lead  ferrocyanide.  More  hydrochloric  acid  makes  the 
allowance  for  the  indicator  too  large  and  too  uncertain  and  so 
impairs  the  accuracy  of  the  method. 

When  lead  is  absent,  for  ores  like  franklinite  and  certain  sul- 
phides containing  no  copper,  it  is  preferable  to  decrease  the  acidity 
to  2  c.c.  of  concentrated  hydrochloric  acid  and  so  decrease  the 
allowance  for  the  end  point. 

To  determine  the  allowance  add  to  a  beaker  a  little  less  than 
200  c.c.  of  water,  10  grams  of  ammonium  chloride  and  6  c.c. 
of  concentrated  hydrochloric  acid  and  warm  to  about  70°  C. 
Place  a  number  of  drops  of  the  uranium  nitrate  solution  on  a 
white  surface,  tile  or  sized  paper.  Run  in  the  ferrocyanide 
solution  a  drop  at  a  time  till,  after  stirring,  the  solution  in  the 
beaker  gives  a  decided  brown  with  the  indicator.  The  amount 
used  should  be  less  than  0.5  c.c.  This  value  must  be  determined 
with  care  as  it  is  subtracted  from  the  burette  reading  in  every 
subsequent  titration. 

Zinc  or  zinc  oxide  can  be  used  for  standardizing.  Really  pure 
zinc  is  very  difficult  to  obtain  as  it  usually  contains  iron,  arsenic 
and  lead  and  often  other  impurities.  Zinc  oxide  can  be  easily 
had  free  from  these  but  should  be  freshly  ignited  and  allowed  to 
cool  in  a  desiccator  to  insure  the  absence  of  carbonates. 

Weigh  out  two  or,  better,  three  portions  of  ignited  zinc  oxide 
each  0.2-0.25  gram ;  dissolve  these  in  No.  3  beakers  in  a  little 
strong  hydrochloric  acid,  dilute  somewhat,  add  sodium  carbonate 
till  a  slight  permanent  precipitate  is  formed  (or  ammonia),  dissolve 
this  in  a  drop  or  two  of  dilute  hydrochloric  acid,  add  the  amount  of 
acid  decided  on  (6  c.c.),  and  10  grams  of  ammonium  chloride; 


DETERMINATION    OF   ZINC   IN    ORES.  69 

dilute  to  about  180  c.c.,  heat  to  70°  C.  and  run  in  the  ferrocyanide 
solution  till  the  indicator  is  affected  as  before. 

The  precipitate  is  white  and  settles  well  when  formed  in  a  hot 
solution  containing  ammonium  chloride,  but  without  considerable 
experience  there  is  no  warning  of  the  end.  Here,  it  is  easy  to  cal- 
culate approximately  how  much  will  be  required  and  so  avoid  the 
tiresome  addition  of  very  small  quantities;  but  in  general  it  is 
better  to  divide  the  solution  roughly  in  half,  then  titrate  one  half, 
adding  a  c.c.  at  a  time,  so  as  to  get  an  idea  of  the  quantity  required. 
If  the  half  took  between  18  and  19  c.c.  (no  color  at  18,  strong  brown 
at  19)  we  can  add  the  other  half  and  run  up  to  35  c.c.  with  safety 
and  then  finish  with  small  additions  till  the  end  is  reached. 

Deduct  the  allowance  for  the  end  point  and  calculate  the  stand- 
ards to  the  value  of  I  c.c.  in  terms  of  zinc.  They  should  not  show 
a  difference  of  more  than  one  in  the  fifth  decimal  place. 

There  is  a  change  in  the  character  of  the  precipitate  which 
seems  to  coincide  with  the  completion  of  the  reaction  given,  and 
so  with  the  ferrocyanide  used  minus  the  allowance ;  this  is  not 
certain  enough  to  be  used  as  an  end  point,  but  after  some  experi- 
ence it  will  indicate  that  the  end  point  will  be  reached  in  a  few 
tenths  of  a  cubic  centimeter. 

There  are  two  very  different  sources  of  zinc:  (i)  Zinc  blende, 
sphalerite,  with  which  may  be  classed  the  other  soluble  ores, 
Smithsonite,  calamine,  etc.,  of  minor  importance.  The  ore  is 
likely  to  contain  also  lead  in  considerable  quantity,  always  iron 
and  often  manganese,  copper,  cadmium  and  sometimes  antimony. 
The  ores  from  Wisconsin,  Missouri,  Virginia  and  the  west  all  come 
under  this  class  of  soluble  ores.  (2)  Franklinite,  which  occurs 
in  large  quantity  in  New  Jersey.  Associated  with  this  mineral, 
there  is  also  willemite  and  a  zinc  spinel.  As  this  ore  is  not  com- 
pletely decomposed  by  acids  and  a  large  amount  of  manganese  is 
present  a  different  treatment  is  required.  It  is  practically  free  from 
copper,  cadmium,  lead  and  antimony. 

Method  for  Blende  and  other  Soluble  Ores.  —  Weigh  out  one  gram 
of  the  finely  ground  ore  and  treat  it  in  a  casserole  or  Erlenmeyer 
flask  with  10-15  c.c.  of  hydrochloric  acid,  I  :  I,  then  add  25  c.c.  of 
strong  nitric  acid  and  boil  down  to  about  lOc.c. ;  add  more  con- 
centrated nitric  acid  and  sodium  or  potassium  chlorate,  a  few 
crystals  at  a  time,  boiling  between  each  addition  to  throw  out  the 
manganese,  and  evaporate  off  all  the  liquid,  but  do  not  bake.  Allow 


70  QUANTITATIVE   ANALYSIS. 

to  cool,  and  when  cold  add  7  grams  of  ammonium  chloride,  15  c.c. 
of  ammonia  and  25  c.c.  of  hot  water ;  boil  for  a  few  minutes  and 
break  up  any  adhering  particles  so  as  to  give  the  excess  of  am- 
monia and  the  ammonium  chloride  every  opportunity  of  taking 
the  zinc  hydroxide  into  solution.  Filter  into  a  flask  or  beaker  and 
wash  the  precipitate  of  ferric  hydroxide,  etc.,  well  with  the  ammo- 
nium chloride  solution,  to  which  a  few  drops  of  ammonia  have  been 
added. 

If  there  is  a  bulky  precipitate  of  ferric  hydroxide  it  will  undoubt- 
edly carry  down  zinc  with  it.  Unless  the  precipitate  is  very  small, 
dissolve  it  through  the  paper  by  hydrochloric  and  sulphurous  acids 
into  a  clean  casserole  and  evaporate  down  with  nitric  acid,  then 
treat  with  chlorate,  etc.,  as  before;  after  washing  the  second  pre- 
cipitate, combine  the  two  filtrates. 

If  the  filtrate  is  blue  copper  is  present.  If  cadmium  is  also  present, 
neutralize  the  filtrate,  heat  and  add  3  c.c.  of  concentrated  hydrochlo- 
ric acid  (no  more)*  and  saturate  with  hydrogen  sulphide  to  precipi- 
tate the  sulphides  of  copper  and  cadmium  which  may  be  contami- 
nated by  some  lead  sulphide,  filter  and  wash,  and  titrate  the  filtrate  as 
already  described.  If  copper  is  present  but  no  cadmium,  it  can  be 
most  easily  removed  by  acidifying  with  10  c.c.  of  hydrochloric  acid 
and  shaking  in  a  flask  with  about  30  grams  of  test  lead  (20  mesh) 
till  the  copper  is  precipitated,  then  decanting,  washing  and  titrating 
as  usual. 

Aluminum  foil  is  not  good  for  this  purpose  as  when  much 
aluminum  is  in  solution  it  is  partially  precipitated  and  makes  the 
end  uncertain.  It  is  also  likely  to  contain  iron.  The  amount  of 
alumina  in  ordinary  ores  does  not  interfere. 

Antimony  is  not  likely  to  be  present.  It  would  be  removed  by 
the  treatment  for  cadmium. 

Notes.  —  Lowf  recommends  the  precipitation  of  the  copper  and 
cadmium  as  sulphides  by  hydrogen  sulphide  in  a  solution  containing 
6  c.c.  of  concentrated  hydrochloric  acid  in  a  volume  of  200  c.c.  and 
the  titration  of  the  zinc  in  the  presence  of  these  sulphides  as  the 
acidity  is  sufficient  to  prevent  the  formation  of  much  lead  sulphide. 

It  has  recently  been  stated  by  Waring;}:  that  cadmium  is  almost 
always  present  in  the  Missouri  zinc  ores  in  quantities  from  .25  to  2 

*The  volume  is  assumed  to  be  about  150  c.c. 

ty.  American  Chemical  Society,  22,  198. 

%  Paper  read  before  N.  Y.  Section  of  the  Am.  Chem.  Soc.,  Oct.  9,  1903. 


DETERMINATION    OF   ZINC   IN    ORES.  71 

per  cent,  and  that  it  is  extremely  difficult  to  effect  a  satisfactory 
separation  of  zinc  from  cadmium  by  hydrogen  sulphide  with- 
out retreating  the  cadmium  sulphide  to  free  it  from  zinc.  Also 
that  the  presence  of  cadmium  is  the  cause  of  a  slight  discolor- 
ation in  the  ferrocyanide  precipitate.  In  order  to  avoid  the  inter- 
ference due  to  cadmium,  Stone's  method  of  precipitating  the  cad- 
mium by  aluminum  foil  in  a  sulphuric  acid  solution  is  used.  This 
will,  of  course,  precipitate  copper  as  well,  but  involves  the  subse- 
quent precipitation  of  the  zinc  as  sulphide,  to  avoid  the  troubles 
caused  by  aluminum  salts.  The  sulphide  is  dissolved  in  hydro 
chloric  acid  and  titrated  under  the  conditions  given.  Two  cubic 
centimeters  of  acid  will  be  enough  here  as  there  is  no  lead  to  be  re- 
tained in  solution  and  the  allowance  for  the  end  point  will  be  less. 
Although  arsenic  does  not  interfere  with  the  titration,  it  prevents 
the  complete  precipitation  of  iron  by  ammonia  in  excess  and  the  ex- 
cess cannot  be  boiled  out  here,  for  then  zinc  would  be  precipitated 
as  Zn(OH2).H2O.  So  Low  recommends  treating  the  ore  with 
bromine  and  hydrochloric  acid  until  the  arsenic  is  expelled  as 
bromide. 

METHOD  FOR  FRANKLINITE. 

Although  nearly  all  the  zinc  in  this  ore  can  be  dissolved  by  a 
treatment  with  concentrated  hydrochloric  acid,  it  is  necessary  to 
fuse  the  residue  to  get  accurate  results.  There  is  also  so  much 
manganese  and  iron  present  that  the  chlorate  and  ammonia  separa- 
tions are  not  satisfactory. 

Fuse  two  grams  of  the  ore  in  platinum  with  about  20  grams  of 
mixed  carbonates,  dissolve  the  melt  in  hydrochloric  acid  and  dehy- 
drate the  silica  if  this  is  to  be  determined.  Neutralize  the  filtrate 
with  a  saturated  solution  of  sodium  carbonate  till  red,  then  add 
pure  barium  carbonate  suspended  in  water  till  the  iron  is  precipi- 
tated (like  the  zinc  oxide  in  manganese  ore).  Make  up  to  an  even 
bulk  in  a  flask,  mix  and  withdraw  portions  for  the  determination  of 
manganese  and  zinc. 

A  variety  of  methods  can  be  used  here;  for  rapid  results,  titrate 
one  portion  for  manganese  by  Volhard's  method,  and  in  another 
after  adding  I  c.c.  of  hydrochloric  acid  I  :  7  titrate  the  total  man- 
ganese and  zinc  by  potassium  ferrocyanide.  (For  details  see  Stone, 
Jour.  Am.  Chem.  Soc.,  17,  473.)  For  more  accurate  work  take  500 
c.c.,  equivalent  to  I  gram  of  ore,  and  precipitate  the  manganese  by 


72  QUANTITATIVE   ANALYSIS. 

bromine  in  an  acetic  acid  solution  as  already  described,  and  in  the 
filtrate,  after  boiling  down  to  expel  acetic  and  hydrobromic  acids, 
titrate  the  zinc  under  the  standard  conditions.  Here  the  2'c.c. 
excess  of  hydrochloric  acid  is  preferable  to  the  6  c.c. 

Notes  on  the  Banum  Carbonate  Separation. — Be  sure  that  the  bar- 
ium carbonate  used  is  free  from  sodium  carbonate,  which  is  used 
to  precipitate  it.  This  is  done  by  boiling  with  a  solution  of  bar- 
ium chloride  for  several  hours ;  the  barium  chloride  gives  barium 
carbonate  with  any  sodium  carbonate  present,  while  the  excess  of 
barium  chloride  and  sodium  chloride  do  no  harm. 

Have  only  chlorides  present ;  add  the  barium  carbonate  in  the 
cold  and  withdraw  portions  or  filter  without  allowing  the  pre- 
cipitate to  stand  long.  Under  these  conditions  the  following  bases 
are  precipitated,  according  to  H.  Rose :  A12O3,  Mn2O8,  Fe2Os, 
Cr2O3,  TiO2,  CdO,  CuO,  As2O5,  Sb2O5,  P2O5  and  others,  either  rare 
or  not  likely  to  be  present. 

On  long  standing,  when  hot,  or  when  present  as  nitrate,  some 
zinc  is  likely  to  be  precipitated.  It  is  well  in  any  case  to  examine 
the  precipitate  for  zinc  and  to  reprecipitate  if  it  is  found. 

In  this  method  the  barium  carbonate  precipitate  can  be  used  for 
the  determination  of  iron  volumetrically  and  the  bromine  precipi- 
tate for  manganese  either  volumetrically  or  gravimetrically. 

GRAVIMETRIC  METHOD. 

An  outline  of  the  plan  to  be  pursued  is:  (i)  Decomposition  of 
the  ore.  (2)  Dehydration  of  the  silica.  (3)  Removal  of  the  fifth  and 
sixth  groups  by  hydrogen  sulphide  in  weakly  acid  solution,  bear- 
ing in  mind  the  ready  solubility  of  lead  sulphide.  (4)  Reoxidation 
on  of  the  iron.  (5)  Precipitation  of  the  iron,  aluminum,  etc.,  by 
either  basic  acetate  or  barium  carbonate.  (6)  Removal  of  the  man- 
ganese by  bromine.  These  operations  have  been  described. 

PRECIPITATION  OF  THE  ZINC  AS  SULPHIDE. 
This  is  necessary  because  of  the  lime  and  magnesia  which  are 
usually  present  from  the  gangue  of  the  ore,  and  which  also  give 
insoluble  phosphates.  Zinc  sulphide  must  be  precipitated  under 
carefully  regulated  conditions  so  that  it  will  filter  rapidly,  as  it  is 
liable  to  oxidize  to  sulphate  on  standing  exposed  to  the  air.  The 
solution  should  be  acid  with  acetic  acid  and  warm,  and  contain 
.about  1 5  grams  of  ammonium  chloride,  which  favors  its  separation 


DETERMINATION    OF   ZINC   IN   ORES.  73 

in  a  flocculent  form  which  filters  well.  Like  many  other  sulphides, 
it  changes  its  form  after  precipitation,  so  it  is  best  to  saturate  the 
solution  with  sulphuretted  hydrogen  gas  and  then  allow  it  to  stand 
in  a  warm  place  over  night  with  a  slow  stream  of  the  gas  passing 
through,  to  prevent  oxidation  and  insure  complete  precipitation. 

Zinc  sulphide  may  be  precipitated  from  an  alkaline  solution,  one 
barely  acid  with  sulphuric  acid,  or  from  solutions  of  organic  acids, 
citric,  formic,  etc.,  and,  best  by  potassium  sulphide,  K2S,  from  an 
alkaline  cyanide  solution  (separation  from  nickel). 

The  sulphide  should  be  washed  with  hydrogen  sulphide  water 
containing  ammonium  chloride  or  acetate  to  prevent  its  resuming 
a  semi-colloidal  condition  and  running  through  the  filter.  It  is 
readily  soluble  in  mineral  acids  and  is  likely  to  be  contaminated 
by  other  sulphides,  particularly  those  of  manganese,  nickel,  cobalt 
and  iron.  There  is  also  danger  of  zinc  sulphide  coming  down 
with  the  lead  sulphide  in  a  very  weakly  acid  solution,  so  that  this 
precipitate  should  be  examined  for  zinc. 

PRECIPITATION  AS  ZINC  AMMONIUM  PHOSPHATE. 

Dissolve  the  zinc  sulphide  in  a  little  dilute  hydrochloric  or 
nitric  acid  into  a  beaker  and  boil  out  the  hydrogen  sulphide. 
Nearly  neutralize  by  ammonia;  dilute  to  about  150  c.c.  and 
warm  on  a  water-bath,  then  add  a  solution  of  ammonium  phos- 
phate, (NH^HPO^,  containing  ten  times  as  much  as  is  required 
to  combine  with  the  zinc.  If  the  precipitate  does  not  form,  add 
ammonia  carefully  until  it  separates.  Warm  on  the  water-bath 
until  the  flocculent  precipitate  changes  completely  to  the  crystal- 
line ZnNH4POi ;  continue  heating  for  fifteen  minutes  longer, 
allow  to  cool  and  filter.  The  precipitate  may  be  treated  in  a 
variety  of  ways,  but  it  is  best  to  weigh  as  ZnNH4PO4,  after  drying 
at  100-105°  C.,  rather  than  to  ignite  to  pyrophosphate.  Filter 
on  paper,  wash  with  a  I  per  cent,  ammonium  phosphate  solution, 
then  with  dilute  alcohol.  Dissolve  the  precipitate  through  into  a 
weighed  platinum  dish  by  dilute  nitric  acid ;  evaporate  to  dryness 
and  weigh  as  ZnNH4PO4  after  drying  at  100-105°  (this  phos- 
phate has  no  water  of  crystallization);  or  filter  on  a  Gooch  cru- 
cible, using  asbestos,  or  on  balanced  filters,  as  already  described. 
The  precipitate  is  readily  soluble  in  acids  or  ammonia,  and  slightly 
soluble  in  very  large  quantities  of  ammonium  salts,  especially  when 
hot.  Microcosmic  salt  can  be  used  with  ammonium  chloride  not 
exceeding  20  grams. 


74  QUANTITATIVE   ANALYSIS. 

Notes. —  The  important  properties  have  been  given.  Any  other 
metal  except  alkali  will  cause  contamination.  On  ignition  to  pyro- 
phosphate,  extraordinary  care  is  required  to  avoid  volatilization  of 
zinc.  The  two  points  to  be  observed  are  a  large  excess  of  reagent  to 
get  a  sufficiently  complete  precipitation  (solubility  product  large) 
and  sufficient  concentration  of  NH4  ions  to  change  the  flocculent 
precipitate  completely  to  ZnNH4PO,.  As  the  (NH4)2HPO4  gives 
both  and  the  excess  is  easily  washed  out,  it  is  the  preferable  re- 
agent. 

ADDITIONAL  REFERENCES. 

Low.     Technical  Estimation  of  Zinc.    J.  American  Chem.  Soc.,  22, 

198,  1900. 
MILLER  AND  HALL.     Notes   on   the   Ferrocyanide   Titration   of 

Zinc.     School  of  Mines  Quarterly,  April,  1900. 
DAKIN.     Determination  of  Zinc  as  Phosphate.     Chemical  News, 

82,  101,  looo. 

For  the  electrolytic  determination  of  zinc  see  Smith's  "  Electro- 
Chemical  Analysis,"  1902. 


LIMESTONE   ANALYSIS. 


75 


CHAPTER  X. 

Limestone  Analysis. 

The  determinations  usually  required  are  silica,  alumina  and  fer- 
ric oxide  (together),  lime  and  magnesia.  When  a  complete  analy- 
sis is  desired  carbon  dioxide,  water,  manganese,  phosphoric  acid, 
sulphur  and  organic  matter  must  be  determined  and  sometimes 
also  barium,  strontium,  chlorine,  fluorine,  potassium  and  sodium. 
Whatever  may  be  required,  the  most  important  determinations  are 
the  first  four,  as  these  indicate  the  composition  with  sufficient  ex- 
actness when  the  limestone  is  used  as  a  flux  in  a  blast  furnace. 
For  this  purpose  the  determination  of  sulphur  and  phosphorus  may 
also  be  needed. 

As  this  "limestone"  analysis,  is  important  also  for  rocks,  clays, 
cement,  water  for  boilers,  etc.,  it  will  be  given  in  considerable 

detail. 

SCHEME  IN  OUTLINE. 

Dissolve  one  gram  in  5  c.c.  cone.  HC1,  I  c.c.  cone.  HNO3  and  20  c.c.  water  with 
heat  in  a  small  casserole,  filter. 


Residue. 

Fuse  +  NaKCO3  dissolve   in   HC1   and 
add  to  filtrate.  1 


Filtrate. 

Evaporate  to  dryness  and  dehydrate 
in  an  air-bath,  take  up  with  H2O  and 
HC1,  heat  and  filter. 


Residue. 
SiOr  etc.  ,  weigh  after 
igniting  with  blast 
lamp.    Then  drive 
off  SiO2    by  HF. 
Fuse   any   residue 
with  NaKCO3  and 
if    A12O3   add     to 
filtrate. 

Precipitate  twice 
Ppt.  Fe(OH)3- 
A12(OH)3± 
P2O5,  ignite  and 
weigh. 

Filtrate. 
:>y  ammonia,  filter,  wash. 

Filtrate.  —  Precipitate 
in  neutral  solution. 
Ppt.  CaC2O4,    wash, 
ignite  and  weigh  as 
CaO  or  CaSO4,  or, 
titrate  the  combined 
oxalic  acid  by  KMn- 
04. 

twice  by  (NHJ2C2O4 

Filtrate.  —Precipitate 
theMgasMgNH4- 
PO4,  ignite  and 
weigh  as  Mg2P2O7 
dissolve  in  HC1  and 
reprecipitate. 

This  scheme  is  without  the  detail  which  is  especially  important 
in  this  analysis,  and  is  given  only  to  show  the  relation  of  the  dif- 
ferent parts  of  the  analysis. 

DETERMINATION  OF  SILICA  AND  OXIDES  OF  IRON  AND  ALUMINUM. 
Weigh  out  exactly  one  gram  of  the  finely  ground  sample,  trans- 
fer it  to  a  small  beaker  and  treat  with  20  c.c.  of  water,  5  c.c.  of 


76  QUANTITATIVE   ANALYSIS. 

concentrated  hydrochloric  acid  and  about  I  c.c.  of  concentrated  ni- 
tric acid,  cover  with  a  watch  glass  and  heat  until  no  further  solution 
takes  place.  Filter  through  a  very  small  paper  into  a  small 
casserole  and  wash  the  residue  once  or  twice  with  water.  Place 
the  filtrate  and  washings  on  the  water  or  steam-bath  to  evaporate. 

If  the  limestone  contained  CaCOs,  MgCOs,  FeCO3  and  SiO2 
only,  the  residue,  after  more  careful  washing,  could  be  ignited  and 
weighed  as  silica,  as  in  this  form  it  is  insoluble  in  acids.  This  is 
sometimes  true  and  saves  much  time  with  the  analysis,  but  if  there 
are  present  silicates  of  lime,  magnesia,  etc.,  these  may  be  insoluble 
or  may  give  gelatinous  silica  which  dissolves  partly,  so  to  ensure 
accurate  results  it  is  necessary  to  fuse  the  residue  to  decompose 
some  silicates  and  also  to  evaporate  and  dehydrate  the  solution  to 
obtain  the  soluble  silica. 

The  nitric  acid  is  added  to  oxidize  the  iron  which  may  be  present 
as  pyrites,  FeS2,  or  as  siderite,  FeCO3. 

While  the  filtrate  is  evaporating,  dry  and  burn  the  filter  contain- 
ing the  residue  in  a  small  platinum  crucible,  then  add  about  six 
times  its  weight  of  mixed  carbonates  and  a  crystal  of  nitrate,  the 
size  of  a  pin  head,  and  fuse  for  about  15  minutes  over  a  Bunsen 
buner.  The  fusion  should  be  perfectly  liquid ;  if  it  is  not,  increase 
the  heat  or  the  flux  or  both  until  a  complete  decomposition  of  the 
insoluble  residue  is  obtained,  bearing  in  mind  the  disadvantage  of 
introducing  into  the  analysis  large  quantities  of  alkali  salts.  When 
cold  remove  the  melt  in  a  cake  if  possible,  dissolve  it  in  hydro- 
chloric acid  and  water  and  add  this  to  the  solution  which  is  evap- 
orating on  the  water-bath.  Continue  the  evaporation  to  dryness, 
stirring  with  a  glass  rod,  when  the  salts  begin  to  crystallize  ;  then 
transfer  to  an  air-bath  and  heat  at  110°  C.  until  there  is  no  more 
smell  of  hydrochloric  acid. 

If  the  insoluble  residue  consisted  of  silicates  of  calcium,  mag- 
nesium or  aluminum  after  fusion  there  are  present  CaCO3,  Mg- 
CO8,  Na2Al2O4,  Na2SiO3  and  the  corresponding  potassium  salts  ; 
on  treating  with  acid  these  give  CaCl2,  MgCl2,  A1C13  and  H2SiO3, 
besides  NaCl  and  KC1.  After  combining  the  two  solutions  we  have 
CaCl2,  MgCl2,  FeCl3,  A1C18,  H2SiO8,  NaCl,  KC1,  HC1.  As  the  cal- 
cium chloride  is  the  predominating  salt,  the  dehydration  of  the 
silica  will  be  easy  on  account  of  its  great  affinity  for  water  (compare 
action  of  sulphuric  acid  in  Brown's  method  for  silicon),  so  that  in 
the  analysis  of  an  ordinary  limestone  it  is  not  necessary  to  repeat 
the  dehydration. 


LIMESTONE   ANALYSIS.  77 

After  dehydration  treat  the  mass  of  salts  with  hydrochloric  acid 
and  water,  heat  to  dissolve  the  salts  of  iron  and  aluminum  and 
filter  out  the  silica,  which  should  be  perfectly  white.  Wash  with 
hot  water,  being  careful  to  use  a  wash  bottle  which  gives  a  very 
fine  stream,  so  as  not  to  dilute  the  filtrate  to  more  than  100  c.c. 
Burn  the  paper  and  ignite  the  silica  over  the  blast-lamp  to  drive 
out  the  last  of  the  water,  cool  in  a  desiccator  and  weigh.  Check 
this  by  driving  off  the  silica  by  hydrofluoric  and  sulphuric  acids  as 
already  described  under  iron  ore.  If  there  should  be  a  residue  it 
is  probably  alumina,  in  any  event  fuse  it  with  a  little  mixed  car- 
bonate, dissolve  the  melt  in  hydrochloric  acid  and  add  this  to  the 
filtrate  from  the  silica. 

To  the  main  filtrate  add  ammonia  in  slight  excess,  and  heat  to 
boiling,  so  that  the  flocculent  precipitate  of  ferric  and  aluminum 
hydroxides  collects  well.  This  contains  any  phosphoric  acid 
present  and  is  probably  contaminated  by  calcium  and  magnesium 
hydroxides.  Allow  to  settle,  and  decant  through  a  filter,  leaving 
all  of  the  precipitate  in  the  bottom  of  the  beaker.  Dissolve  the 
precipitate  in  dilute  hydrochloric  acid  and  reprecipitate  by  am- 
monia, heat  again,  filter  and  wash  till  free  from  chlorides  by  boiling 
water,  avoiding  unnecessary  dilution  of  the  filtrate.  Filter  without 
delay  as  the  alkaline  solution  will  absorb  carbon  dioxide  from  the 
air  and  so  cause  contamination  due  to  calcium  carbonate.  The 
remedy  would  be  to  redissolve  in  acid,  boil  out  the  carbon  dioxide 
and  reprecipitate.  Burn  the  paper,  etc.,  moisten  the  residue  with 
nitric  acid  and  ignite  finally  by  the  blast-lamp  and  weigh  the  com- 
bined oxides  of  iron  and  alumina. 

PRECIPITATION  OF  CALCIUM  OXALATE. 

The  filtrate,  containing  CaCl2,  MgCl2,  KC1,  NaCl,  NH4C1  etc.,  is 
made  decidedly  acid  with  hydrochloric  acid ;  then  enough  oxalic 
acid  is  added  to  combine  with  all  the  lime  and  the  solution  is 
heated  to  boiling. 

To  the  boiling  solution  a  few  drops  of  methyl-orange  are  added 
and  then  gradually  and  with  frequent  pauses  dilute  ammonia,  till 
the  indicator  changes  color.  The  neutralization  should  take  half 
an  hour,  then  a  considerable  excess  of  ammonium  oxalate  is  added 
and  the  precipitate  allowed  to  stand  for  four  hours.  Next  filter 
and  wash  with  a  I  per  cent,  solution  of  ammonium  oxalate.*  Al- 

*  Richards,  Z.  Anorg.  Chemie,  28,  88. 


78  QUANTITATIVE   ANALYSIS. 

though  if  these  conditions  are  carried  out  very  carefully  it  is  possi- 
ble to  obtain  a  very  complete  separation  of  calcium  from  magne- 
sium by  one  precipitation,  it  is  safer  to  redissolve  the  precipitate  in 
hydrochloric  acid,  after  decanting  or  filtering,  and  to  reprecipitate 
as  before  by  neutralizing  with  ammonia  and  then  adding  ammo- 
nium oxalate. 

The  main  difficulty  in  precipitating  calcium  oxalate  is  the  con- 
tamination due  to  magnesium  oxalate.  Although  this  is  a  per- 
fectly soluble  salt  it  is  carried  down  by  the  calcium  oxalate  (adsorp- 
tion) and  not  readily  removed  by  washing.  An  alkaline  solution 
is  most  favorable  to  this  contamination  ;  so,  if  to  the  acid  solution 
we  add  enough  oxalic  acid  to  combine  with  the  lime  and  then 
neutralize  gradually,  the  calcium  oxalate  will  be  formed  in  as  acid 
a  solution  as  possible  and  also  in  one  in  which  it  is  somewhat 
soluble,  hence  it  will  be  free  from  magnesium  oxalate  and  also  in 
large  crystals  which  can  be  easily  filtered  and  washed.  The  indi- 
cator, methyl-orange,  turns  before  an  excess  of  ammonia  has  been 
added.  If  we  stopped  at  this  point  we  would  not  get  complete 
precipitation  of  the  calcium  as  there  is  not  yet  present  any  consid- 
erable excess  of  ammonium  oxalate,  so  then  an  excess  of  ammo- 
nium oxalate  is  added,  which  converts  the  magnesium  largely  to 
oxalate,  and  by  the  mass  action  of  the  C2O4  ions  the  solubility  prod- 
uct of  calcium  oxalate  is  exceeded,  the  Ca  ions  are  driven  out  of 
solution,  and  the  precipitation  of  the  calcium  oxalate  is  complete. 
Now  that  the  magnesium  is  present  largely  as  oxalate,  we  must 
not  wait  too  long  before  filtering,  as  it  has  been  found  that  the 
magnesium  oxalate  increases  on  the  precipitated  calcium  oxalate. 
As  the  calcium  oxalate  is  very  slightly  soluble  in  hot  water,  it  is 
washed  with  a  solution  containing  an  ion  in  common,  I  per  cent, 
ammonium  oxalate. 

If  the  calcium  is  to  be  determined  gravimetrically,  the  ammo- 
nium oxalate  need  not  be  removed  ;  if  a  volumetric  method  (potas- 
sium permanganate)  is  to  be  used  this  must  be  washed  out  with 
cold  water. 

When  calcium  oxalate  is  ignited  it  gives  a  mixture  of  carbonate 
and  oxide ;  this  can  be  heated  by  a  blast-lamp  for  half  an  hour  or 
more  until  constant  weight  is  obtained  and  the  resulting  calcium 
oxide  weighed.  Great  care  must  be  observed  to  expel  all  the 
carbon  dioxide  and  to  avoid  any  reabsorption  of  this  or  of  water 
from  the  air,  by  cooling  in  a  desiccator  and  weighing  quickly. 


LIMESTONE   ANALYSIS.  79 

After  burning  the  paper,  etc.,  the  residue  can  be  converted  to 
sulphate  by  moistening  with  dilute  sulphuric  acid  and  heating  care- 
fully over  a  Bunsen  burner  (no  blast)  till  the  excess  is  expelled, 
then  weighing  when  cold  and  repeating  the  treatment  until  a  con- 
stant weight  is  obtained. 

When  the  oxalic  acid  combined  with  the  calcium  is  to  be  ti- 
trated by  permanganate,  proceed  as  follows :  Dissolve  the  pre- 
cipitate through  the  filter  with  the  least  possible  quantity  of  hot 
dilute  hydrochloric  acid  into  a  large  beaker,  dilute  with  warm 
water,  add  an  excess  of  concentrated  sulphuric  acid  (5—6  c.c.),  ten 
grams  of  manganous  sulphate,  and  titrate  at  about  65°  C.  Or  dis- 
solve through  the  paper  in  very  dilute  sulphuric  acid,  add  more 
sulphuric  acid,  warm  and  titrate. 

Besides  the  properties  of  calcium  oxalate  already  mentioned, 
like  barium  sulphate,  when  formed  in  a  cold  solution,  it  is  very 
fine  and  runs  through  the  filter.  It  is  dissolved  by  mineral  acids 
and  is  slightly  soluble  in  acetic  acid.  It  should  be  precipitated  in 
a  solution  containing  no  salts  other  than  those  of  magnesium  and 
the  alkalies,  as  it  would  be  contaminated  by  barium  oxalate,  man- 
ganous oxalate,  etc. 

MAGNESIUM  DETERMINATION. 

The  filtrate  should  be  about  200  c.c.  in  volume,  and  will  contai 
a  large  amount  of  ammonium  chloride  and  oxalate.  If  the  amount 
of  magnesium  is  considerable  (dolomite)  it  can  be  precipitated  in 
this  solution  by  adding  sodium  or  ammonium  phosphate  and  then 
an  excess  of  ammonia,  etc.,  as  already  explained.  After  igniting 
and  weighing  the  magnesium  pyrophosphate,  it  is  best  to  dissolve 
it  in  dilute  hydrochloric  acid  and  to  weigh  any  residue  of  silica 
with  the  crucible.  Then  subtract  this  weight  instead  of  the  original 
weight  of  the  crucible,  as  the  ammonia  salts  are  likely  to  cause 
contamination  of  the  precipitate  by  silica  from  the  beakers. 

If  the  amount  of  magnesia  is  small,  as  is  usually  the  case,  it  will 
not  come  down  satisfactorily  in  the  presence  of  the  relatively  large 
amounts  of  ammonia  salts.  Concentrate  the  solution  as  far  as 
possible  in  a  beaker,  then  transfer  to  a  platinum  dish  and  evap- 
orate to  dryness.  If  the  salts  crawl  up  the  sides,  heat  the  upper 
edge  of  the  dish  instead  of  the  bottom,  best  by  putting  a  top  on 
the  burner  which  gives  a  number  of  small  flames  from  the  sides. 
Then  ignite  to  drive  off  the  ammonia  salts,  take  up  the  residue 


8o  QUANTITATIVE   ANALYSIS. 

with  dilute  hydrochloric  acid,  filter  if  necessary  (to  remove  dust  and 
silica)  and  determine  the  magnesia  as  usual. 

A  very  good  method  of  getting  rid  of  ammonium  chloride  is  to 
add  to  the  very'concentrated  solution  in  a  casserole  (just  as  the 
salts  are  beginning  to  separate)  strong  nitric  acid  and  continue  the 
evaporation.  The  ammonium  chloride  breaks  up  and  is  expelled, 
probably  according  to  the  following  reaction  : 

NH4Q  +  HN03  =  HC1  +  2H20  +  N2O, 
while  the  excess  of  nitric  acid  helps  to  decompose  the  oxalates. 

When  the  oxalates  are  not  destroyed  and  sodium  phosphate  is 
used  as  a  precipitant,  the  magnesium  ammonium  phosphate  must 
be  washed  very  thoroughly  to  remove  the  sodium  oxalate. 

EFFECT  OF  BARIUM,  MANGANESE  OR  PHOSPHORIC  ACID. 

If  the  limestone  contained  a  little  barium  carbonate  and  consider- 
able pyrites,  barium  sulphate  would  be  formed,  which  would  con- 
taminate the  silica.  After  driving  off  the  silica,  fuse  the  residue  as 
usual  and,  if  a  precipitate  is  reformed  on  acidifying,  filter  and  add 
only  the  clear  solution  to  the  main  filtrate.  It  might  happen  that 
the  barium  carbonate  was  in  excess  of  the  sulphur,  so  that  only  a 
portion  would  be  precipitated  as  barium  sulphate  while  some  would 
come  down  as  oxalate  and  the  rest  as  phosphate.  In  such  a  case 
add  dilute  sulphuric  acid  drop  by  drop  before  filtering  off  the 
silica  so  as  to  precipitate  all  the  barium,  avoiding  much  excess, 
so  as  not  to  form  calcium  sulphate  which  would  contaminate  it. 
Then,  after  driving  off  the  silica,  the  barium  sulphate  can  be 
weighed  if  pure  or  fused  and  reprecipitated. 

Should  there  be  manganese  present  it  will  contaminate  the  am- 
monia precipitate  unless  the  precipitation  is  repeated,  and  also  the 
calcium  oxalate.  It  is  possible  to  precipitate  calcium  as  oxalate 
in  the  presence  of  iron  but  not  in  that  of  manganese  (see  slag  anal- 
ysis) so  that  the  manganese  must  be  removed  before  the  precipi- 
tate of  calcium  oxalate.  This  can  be  done  as  follows : 

1.  After  several  ammonia  precipitations  add  bromine  water  and 
ammonia,  warm  and  filter  out  the  higher  hydrated  oxide  of  man- 
ganese. 

2.  Saturate  the    filtrate,  slightly  alkaline  with  ammonia,  with 
hydrogen  sulphide  and  filter  out  the  manganous  sulphide. 

3.  Substitute  the  basic  acetate  for  the  ammonia  precipitation  and 
take  the  manganese  out  of  the  filtrate  by  either  bromine  or  by  hy- 
drogen sulph'de. 


LIMESTONE   ANALYSIS.  81 

The  determination  of  manganese  has  been  described. 

There  are  cases  in  which  the  amount  of  phosphoric  acid  is  more 
than  enough  to  combine  with  the  iron  or  iron  and  aluminum  pres- 
ent, so  that  the  ammonia  precipitate  will  also  contain  calcium  as 
phosphate,  which  can  not  be  removed  by  solution  and  reprecipi- 
tation.  In  such  a  case  add  a  known  amount  of  iron  as  ferric  chlo- 
ride, which  shall  furnish  an  excess  over  that  required  to  combine 
with  the  phosphoric  acid,  and  precipitate  with  ammonia  as  usual. 
All  the  lime  will  be  in  the  filtrate  and  the  ferric  oxide  from  the 
iron  solution  added  must  be  subtracted  from  the  weight  of  the  total 
alumina  and  ferric  oxide. 

APPLICATIONS  OF  THE  "  LIMESTONE"  ANALYSIS. 

The  most  important  variations  when  this  analysis  is  to  be  ap- 
plied to  a  rock  are : 

i.  Fuse  the  entire  rock  with  Na2CO3  or  NaKCO3,  because  so 
little  will  dissolve  in  acid  that  the  treatment  is  not  advisable.  • 

2..  Dehydrate  the  silica  by  evaporation  on  a  water-bath  twice, 
or  if  very  high  in  silica  (acid  rock),  three  times.  The  reason  for 
this  is  seen  when  we  compare  the  composition  of  limestone  with 
that  of  rock.  Limestone  contains  perhaps  2-3  per  cent,  of  silica 
and  45-50  per  cent,  of  lime.  Rock,  60  per  cent,  or  even  80  per 
cent,  of  silica  and  a  small  amount  of  lime.  So  that  if  one  hun- 
dredth of  the  silica  present  escapes  the  first  dehydration,  the  error 
is  0.6-0.8  per  cent. 

3.  Always  look  for  manganese  in  a  rock,  a  green  fusion  due  to 
manganate  when  nitrate  is  added  to  the  mixed  carbonates  in  the 
fusion,  but  not  always  formed  without  it. 

With  clays  the  treatment  is  similar  to  that  given  for  rocks,  but 
here  the  percentage  of  alumina  is  higher  and  that  of  lime  and 
magnesia  lower,  so  that  the  double  dehydration  of  the  silica  is 
necessary,  and  also  the  refusion  of  any  residue  left  after  driving  off 
the  silica,  which  will  usually  be  alumina,  possibly  also  titanic  ox- 
ide. The  aluminum  and  ferric  hydroxides  must  be  very  carefully 
precipitated  in  the  presence  of  ammonium  chloride  and  with  but 
a  slight  excess  of  ammonia. 

With  rock,  clay  or  cement,  it  is  not  enough  to  obtain  the  com- 
bined per  cent,  of  A12O3  and  Fe2O3;  the  iron,  ferrous  or  ferric,  is 
also  required.  This  can  be  done  as  follows :  After  igniting  and 
weighing  the  combined  oxides,  fuse  them  for  at  least  forty-five 


82  QUANTITATIVE   ANALYSIS. 

minutes  at  a  low  heat  with  8-10  times  their  weight  of  potassium 
bisulphate  or  potassium  pyrosulphate,  then  at  the  end  add  concen- 
trated sulphuric  acid  to  reconvert  the  potassium  sulphate  to  bisul- 
phate. This  changes  the  iron  and  aluminum  to  sulphates  and  at 
the  same  time  dehydrates  any  silica  which  has  previously  escaped 
and  has  precipitated  with  the  hydroxides.  Dissolve  the  melt  in 
water  and  sulphuric  acid,  filter,  add  the  silica  to  the  main  portion, 
reduce  the  iron  in  the  filtrate  bypassing  it  through  a  reductor  and 
titrate  by  permanganate. 

For  cements,  which  often  contain  about  22  per  cent,  of  silica 
and  60  per  cent,  of  lime,  two  evaporations  for  silica,  and  the  sepa- 
rate percentages  of  oxides  of  iron  and  aluminum,  constitute  the 
important  variations  from  the  "  limestone  "  analysis  described. 

For  the  best  information  on  rock  analysis  see  Hillebrand,  Bulle- 
tin of  the  U.  S.  Geological  Survey,  No.  176.  For  cement  analysis, 
report  of  committee,/.  Society  of  Chemical  Industry,  Vol.  XXL,  pp. 
12-30,  1902,  and  Hillebrand,  J.  AmericanChetn.  Soc.,  XXV.,  1180, 
1903. 

This  discussion  also  covers  the  main  portion  of  slag  analysis ; 
the  composition  of  slag  varies  within  wide  limits,  and  there  may 
be  present  any  of  the  common  or  rare  elements.  But  bearing  in 
mind  that  the  fifth  and  sixth  groups  are  taken  out  after  the  silica, 
and  the  principles  of  the  "limestone"  analysis,  the  special  meth- 
ods given  later  for  typical  slags  will  easily  be  understood. 

DETERMINATIONS  OF  CARBON  DIOXIDE,  SULPHUR  AND  PHOSPHORUS. 

The  other  determinations  in  limestone  are  made  on  separate  por- 
tions. 

Carbon  dioxide  is  either  found  by  loss  or  by  direct  weight,  the 
methods  are  given  in  the  text-books.*  A  rapid  method  is  to  fuse 
about  four  grams  of  borax  glass  (Na2B4O7)  in  a  platinum  crucible, 
and  when  cold  weigh ;  place  about  one  gram  of  the  dried  lime- 
stone on  the  top  of  the  borax  glass  and  reweigh.  Then  fuse  with 
a  Bunsen  burner  till  no  more  gas  is  given  off  (no  blast),  cool  and 
weigh.  The  loss  in  weight  is  carbon  dioxide,  provided  there  is  no 
moisture  or  organic  matter  present.  The  method  is  only  approx- 
imate, as  borax  glass  is  slightly  volatile  and  gives  total  carbon  di- 
oxide, water  and  organic  matter,  when  the  latter  are  present. 

*  Cairn's  "Quantitative  Analysis,"  pp.  33-37. 


LIMESTONE   ANALYSIS.  83 

The  reaction  is  Na2B4O7  +  CaCO3  =  Na2B2O4  +  CaB2O4  +  CO2. 

Sulpliur. — Unless  barium  sulphate  is  present,.dissolve  five  grams 
of  a  sample  in  15  c.c.  concentrated  hydrochloric  acid  and  5  c.c. 
concentrated  nitric  acid  and  15  c.c.  of  water  in  a  casserole,  evap- 
orate, add  more  hydrochloric  acid  and  evaporate  to  dryness  to  ex- 
pel the  nitric  acid  and  dehydrate  the  silica ;  take  up  with  hydro- 
chloric acid  and  water,  boil  and  filter ;  neutralize  the  filtrate  with 
ammonia  so  that  it  is  just  acid  with  hydrochloric  and  precipitate 
the  sulphate  by  barium  chloride  as  usual. 

If  barium  sulphate  is  present,  fuse  the  residue  with  mixed  car- 
bonates, leach  with  water,  filter  out  the  barium  carbonate  and  add 
the  filtrate  to  the  main  solution,  dehydrate  and  precipitate  as  usual. 

Phosphorus. —  Dissolve  5  grams  in  40  c.c.  of  dilute  nitric  acid, 
evaporate  to  dryness,  take  up  with  nitric  acid  and  water,  filter,  neu- 
tralize the  excess  of  nitric  acid  by  ammonia,  and  precipitate  as  am- 
monium phosphomolybdate,  etc..  as  in  iron  ore.  If  the  iron  and 
alumina  are  low,  the  molybdate  precipitation  can  be  omitted.  Dis- 
solve 5  grams  in  hydrochloric  acid,  evaporate,  bake,  take  up  with 
hydrochloric  acid  and  water,  filter ;  to  the  filtrate  add  2-3  grams 
of  citric  acid,  to  prevent  the  precipitation  of  aluminum  or  ferric 
hydroxides  or  calcium  phosphate,  neutralize  with  ammonia  and 
precipitate  by  magnesia  mixture  direct. 

Sulphur  and  phosphorus  are  objectionable  when  the  limestone 
is  used  as  a  flux  for  iron  ores. 


84  QUANTITATIVE   ANALYSIS. 


CHAPTER   XL 

The  Determination  of  Copper  in  Ores  and  Mattes. 

Among  the  many  methods  which  have  been  proposed  for  the 
determination  of  copper  the  electrolytic,  iodide  and  cyanide  are  of 
the  greatest  importance  and  the  thiocyanate  and  colorimetric 
methods  deserve  mention. 

As  the  method  of  solution  is  the  same  for  all  these  methods,  it 
will  be  described  first. 

For  ores,  weigh  out,  depending  on  the  richness,  from  I  to  5 
grams  of  the  very  finely  ground  sample,  so  as  to  obtain  about 
150  milligrams  of  copper.  Treat  this  in  a  covered  casserole  or 
Erlenmeyer  flask  (200  c.c.)  with  20  c.c.  concentrated  nitric  acid, 
5  c.c.  concentrated  hydrochloric  acid  and  5  c.c.  concentrated  sul- 
phuric acid  ;  heat  until  all  the  copper  has  dissolved  and  then  evap- 
orate to  dense  white  fumes  of  SO3  (at  this  point  the  blue  color  will 
have  disappeared,  no  water  being  present),  allow  to  cool;  dilute 
with  water  and  heat  to  dissolve  ferric  sulphate,  etc. ;  filter  out  the 
residue,  which  consists  of  silica,  silicates  and  the  insoluble  sul- 
phates of  lead,  barium,  etc.,  wash  this  residue  with  hot  water 
thoroughly,  taking  care  to  avoid  unnecessary  dilution. 

This  treatment  will  dissolve  the  copper  in  all  ordinary  ores,  but 
if  it  is  present  as  silicate  (chrysocolla  or  slags)  the  residue  should 
be  fused  with  mixed  carbonates  to  ensure  complete  decomposition. 

For  mattes,  use  0.25-0.5  gram  and  half  the  quantities  of  nitric 
and  hydrochloric  acids  and  about  4  c.c.  of  sulphuric  acid.  Alloys 
such  as  brass,  german  silver,  etc.,  can  be  treated  in  the  same  way 
when  it  is  desired  to  separate  out  the  lead  as  sulphate ;  or  dis- 
solved in  nitric  acid  alone,  depending  on  the  methods  to  be  used 
for  the  subsequent  separations.  With  bronze  nitric  acid  alone  is 
used  followed  by  long  boiling  in  a  very  dilute  solution,  so  as  to 
separate  out  the  tin  as  completely  as  possible,  as  rnetastannic 
acid.  This  often  contains  copper  which  is  separated  from  tin 
by  digesting  the  residue  on  a  water-bath  with  potassium  sulphide 
(not  ammonium  sulphide).  This  also  applies  to  brass  and  german 
silver  when  they  contain  tin. 


THE   DETERMINATION    OF    COPPER.  85 

ELECTROLYTIC  METHOD. 

The  sulphuric  acid  solution  containing  CuSO4,Fe2(SOJ3,  etc.,  be- 
sides the  possible  impurities,  arsenic,  antimony,  bismuth,  can  be 
electrolyzed  directly,  provided  there  is  not  too  great  an  excess  of 
sulphuric  acid  present.  2—3  c.c.  of  concentrated  acid  in  a  volume 
of  about  100  c.c.  is  a  suitable  quantity ;  if  this  is  exceeded  a  por- 
tion can  be  neutralized  by  ammonia.  If  the  copper  is  from  a 
chalcopyrite  there  will  be  a  considerable  quantity  of  ferric  sulphate 
present,  and  the  separation  of  copper  succeeds  best  under  the 
conditions  given.  It  is  impracticable  to  precipitate  the  iron  by 
ammonia  before  electrolysis  as  the  ferric  hydroxide  always  carries 
down  copper.  If  difficulty  is  encountered  in  depositing  the  last 
traces  of  copper,  the  solution  after  electrolysis  can  be  made  alka- 
line by  ammonia  and  when  there  are  only  traces  of  copper  pres- 
ent, the  amount  held  by  the  precipitate  can  be  neglected.  In  the 
filtrate  the  copper  can  be  determined  colorimetrically  or  the  solu- 
tion made  acid  again  by  sulphuric  acid  and  the  electrolysis  con- 
tinued. 

The  colorimetric  estimation  consists  in  comparing  the  shade  of 
blue  in  the  ammoniacal  solution  with  the  color  of  standards  made 
up  containing  known  amounts  of  copper  in  the  same  volume  and 
having  the  same  excess  of  ammonia  and  at  the  same  temperature. 
For  the  details  of  this  method  see  Heath,  J.  Am.  Chem.  Soc.t  Vol. 
19,  p.  24,  1 897,  and  Smith,  Trans.  American  Institute  Mining  Engi- 
neers, 30,  851,  1901.  When  arsenic  and  antimony  are  present  in 
large  quantities,  the  method  described,  or  any  other  electrolytic 
method,  fails  to  give  accurate  results,  as  some  of  these  impurities 
are  deposited  with  the  copper.  This  may  be  remedied  by  roast- 
ing the  material  before  dissolving  (after  weighing),  or  by  repeated 
evaporations  with  bromine,  or  by  heating  the  precipitated  sulphides 
with  a  solution  of  sodium  or  potassium  sulphide,  filtering  and  then 
dissolving  the  copper  sulphide  in  nitric  acid. 

When  the  arsenic  and  antimony  are  present  only  in  exceedingly 
small  quantities  the  presence  of  nitric  acid  prevents  or  retards  their 
deposition,  so  that  the  best  conditions  for  the  electrolysis  of  a  cop- 
per matte  are,  as  regards  acidity,  2-3  c.c.  of  sulphuric  acid  1.84  sp. 
gr.  and  2  c.c.  nitric  acid  1.42  sp.  gr.  in  a  volume  of  about  150  c.c. 

Bismuth  is  the  most  troublesome  metal  in  connection  with  all 
the  methods  for  copper;  it  is  not  removed  by  roasting,  and 
although  not  easily  precipitated  completely  by  the  current,  it  al- 


86  QUANTITATIVE   ANALYSIS. 

ways  contaminates  the  copper  when  present,  often  without  causing 
any  perceptible  discoloration  of  the  deposit.  If  present,  dissolve 
the  deposited  copper  in  nitric  acid,  add  ammonia  in  excess,  then 
ammonium  carbonate,  dilute  to  150  c.c.  and  boil.  The  bismuth  is 
precipitated  as  a  basic  carbonate,  contaminated  by  copper;  by 
resolution  in  nitric  acid  and  reprecipitation  it  can  be  obtained  pure  ; 
then  washed,  ignited  and  weighed  as  Bi2O3.  The  calculated  weight 
of  bismuth  is  deducted  from  the  weight  of  the  deposit. 

When  the  bismuth  is  present  in  large  amount,  or  when  it  is  also 
to  be  determined,  the  method  described  by  Riederer,  J.  Am.  Chem. 
Soc.,  Vol.  XXV.,  p.  919,  1903,  can  be  employed. 

The  special  apparatus  required  for  the  determination  of  copper 
cpnsists  of  platinum  electrodes  and  a  suitable  stand. 

The  anode  is  usually  made  of  a  stout  platinum  wire,  bent  into  a 
spiral  when  a  cylindrical  cathode  is  used  or  coiled  into  a  disc  when 
a  platinum  dish  is  used.  The  cylindrical  cathode  is  most  con- 
venient when  many  determinations  are  made  at  the  same  time  ; 
it  should  be  open  at  the  side  so  as  to  allow  the  circulation  of  the 
electrolyte.  Both  electrodes  should  be  thoroughly  clean,  free  from 
deposited  metal,  grease  or  dust.  This  is  obtained  by  treatment 
with  nitric  acid  or  with  alcohol  and  then  drying  above  the  flame 
of  a  burner. 

The  cathode  is  then  weighed  and  connected  with  the  negative 
pole  of  the  battery  or  source  of  electricity,  while  the  anode  is  con- 
nected with  the  positive  pole.  With  cylindrical  electrodes  the  cop- 
per solution  is  placed  in  a  small  but  tall  beaker  and  the  cathode 
adjusted  so  that  about  half  an  inch  is  out  of  the  liquid,  and  the 
beaker  covered  by  a  divided  watch  glass  or  two  pieces  of  mica  to 
keep  out  dust  and  prevent  loss  by  spattering.  With  a  dish,  a  watch 
glass  with  a  hole  in  the  center  for  the  anode  to  pass  through,  is 
used  as  a  cover. 

The  area  of  the  cathode  should  be  about  ten  square  inches  and 
the  current  1.5-2  volts  and  0.1-0.2  ampere.  It  is  turned  on  and 
the  copper  allowed  to  deposit  for  from  twelve  to  fifteen  hours,  then 
if  the  electrolyte  is  colorless  the  cathode  is  lowered  about  one 
fourth  inch  so  as  to  expose  a  fresh  surface  of  platinum  for  deposi- 
tion and  the  electrolysis  is  continued  for  an  hour  longer.  When 
no  more  copper  is  deposited,  a  few  c.c.  of  the  solution  are  with- 
drawn by  a  pipette  and  tested  with  freshly  prepared  hydrogen  sul- 
phide water  on  a  white  surface.  This  test  is  much  more  delicate 
than  the  blue  color  with  ammonia. 


THE   DETERMINATION    OF    COPPER.  87 

As  there  is  nitric  acid  present  the  cathode  must  be  removed 
while  the  current  is  still  passing,  otherwise  the  nitric  acid  would 
immediately  begin  to  redissolve  copper.  This  can  be  done  by 
siphoning  out  the  contents  of  the  dish  and  at  the  same  time  adding 
water,  until  the  solution  is  too  dilute  to  attack  the  deposit,  or  if 
the  electrolysis  is  done  in  a  beaker,  the  block  beneath  it  can  be 
removed  and  a  beaker  of  water  substituted,  then  the  cathode  is 
allowed  to  drop  into  the  water. 

The  deposited  copper  must  be  dried  without  oxidation ;  so  it  is 
next  rinsed  off  with  alcohol  to  displace  the  water,  then,  when  great 
precautions  are  required,  with  ether  and  is  dried  at  a  very  gentle 
heat — such  as  can  easily  be  borne  by  the  hand — so  as  not  to  oxidize 
the  deposit.  When  cold  it  is  allowed  to  stand  in  the  balance  room 
for  about  ten  minutes  and  then  weighed. 

For  the  electrolytic  assay  as  applied  to  refined  copper,  see 
Heath,  Trans.  A.  /.  M.  E.t  July,  1899. 

The  behavior  of  the  elements  likely  to  be  present,  under  the 
conditions  given  is  briefly  as  follows :  Iron  does  not  interfere  unless 
insufficient  sulphuric  acid  is  present.  Then  the  nitric  acid  be- 
comes reduced  to  ammonia,  which  precipitites  ferric  hydroxide. 
In  the  directions  given,  the  amount  of  sulphuric  acid  is  sufficient 
to  neutralize  all  the  ammonia  formed,  even  if  the  nitric  acid  is  com- 
pletely reduced. 

Nickel  and  cobalt  do  not  interfere  in  a  strongly  acid  solution. 
They  are,  however,  deposited  in  an  ammoniacal  solution,  if  the  cur- 
rent is  strong.  Zinc  requires  the  presence  of  a  strong  acid  to 
prevent  its  precipitation,  i.e.,  nitric;  it  may  be  deposited  in  an 
extremely  weak  sulphuric  acid  solution  or  readily  from  solutions 
of  organic  acids,  like  acetic,  citric,  lactic,  etc.  So  that  if  the  elec- 
trolysis is  prolonged  and  the  free  nitric  acid  reduced  zinc  may 
be  deposited.  Manganese  does  not  deposit  as  metal,  but  goes  to 
the  anode  as  peroxide ;  it  is  sometimes  oxidized  higher  to  per- 
manganic acid  which  gives  a  color  to  the  solution  about  the 
anode.  Lead  in  traces  escapes  precipitation  as  sulphate  and  ap- 
pears on  the  anode  as  PbOaV  Bismuth  contaminates  the  copper 
and  also  goes  to  the  anode~as  peroxide.  Arsenic  and  antimony 
are  liable  to  contaminate  the  copperas  explained. 

Silver  will  be  removed  as  chloride,  unless  the  digestion  with  con- 
centrated sulphuric  acid  is  very  long,  then  it  is  partly  changed  to 
sulphate.  If  present,  it  will  deposit  completely  with  the  copper; 


88  QUANTITATIVE   ANALYSIS. 

but  is  easily  removed  by  a  drop  of  a  chloride.  Gold,  platinum, 
etc.,  would  be  deposited,  but  are  not  likely  to  be  present  in  suffi- 
cient quantity  to  influence  the  results. 

In  general  salts  are  objectionable,  although  in  some  cases  they 
are  added.  For  example,  Classen  precipitates  copper  and  other 
metals  from  a  solution  containing  large  amounts  of  ammonium 
oxalate.  Hydrochloric  acid  and  chlorides  should  be  absent,  as 
they  cause  the  deposit  to  be  spongy. 

For  a  detailed  discussion  of  the  quantitative  deposition  of  metals 
by  electrolysis  see  "  Electrochemical  Analysis,"  by  Prof.  E.  F. 
Smith,  1902. 

It  is  of  the  greatest  importance  that  a  dense  firmly  adherent  de- 
posit be  obtained,  free  from  impurities  ;  aside  from  the  chemical 
conditions,  the  character  of  the  current  has  much  influence  on  that 
of  the  deposit. 

To  describe  the  current  we  must  know  the  voltage  and  amper- 
age ;  the  latter  is  often  given  as  current  density,  that  is,  the  num- 
ber of  amperes  per  100  sq.  cm.  of  cathode  area.  ND.ioo  =  0.2 
means  0.2  amperes  for  each  100  sq.  cm.  of  the  submerged  area  of 
the  cathode  on  which  metal  is  deposited. 

The  amperes  determine  the  rate  of  deposit,  according  to  Fara- 
day's law,  but  in  quantitative  analysis  the  character  is  of  greater 
importance  than  the  rate,  so  for  copper  a  low-current  density  is 
used,  0.1-0.15  ampere,  because  a  stronger  current  (except  in 
special  cases)  is  liable  to  give  a  dark,  spongy  and  non-adherent 
deposit,  which  is  difficult  to  dry  without  oxidation,  and  to  weigh 
without  loss. 

The  voltage  should  also  be  low  enough  to  overcome  the  coun- 
ter-electromotive force  of  the  solution  and  its  resistance ;  for  copper 
about  1.5  volts,  but  not  a  high  voltage,  as  it  tends  to  increase  the 
impurity  of  the  deposit.  The  best  current  for  electrolytic  work  can 
be  obtained  from  storage  batteries,  or  primary  batteries ;  but  as  the 
lighting  circuits  are  more  convenient,  they  may  be  used  by  insert- 
ing a  suitable  resistance. 

The  counter-electromotive  force  necessary  to  deposit  a  metal  can 
be  calculated  from  the  heat  of  formation  of  the  molecule,  and  the 
results  so  obtained  agree  well  with  those  found  by  experiment. 
But  the  question  may  well  be  asked,  if  salts,  such  as  copper  sul- 
phate, are  already  ionized  in  solution,  why  is  all  this  energy  re- 
quired to  pull  the  copper  sulphate  apart?  The  answer  is  found  in 


THE   DETERMINATION    OF    COPPER.  89 

Nernst's  solution-tension  theory.  This  is,  briefly,  that  each  metal 
has  a  certain  power  of  forcing  its  atoms  into  solution  as  ions;  just 
as  a  liquid  continues  to  evaporate  at  its  surface  till  the  pressure  of 
the  vapor  becomes  equal  to  the  vapor-tension  of  the  liquid,  so  the 
metal  sends  ions  into  solution  till  the  osmotic  pressure  of  these  ions 
becomes  equal  to  the  solution-tension  of  the  metal.  Therefore,  in 
order  to  separate  out  the  copper  ions  in  the  form  of  metallic  copper,  a 
certain  electrical  pressure  or  intensity  of  current  is  required,  so  that 
the  sum  of  this  and  the  osmotic  pressure  shall  exceed  the  solution 
tension. 

These  differences  in  solution  tension  for  different  ions  can  be 
found  in  the  books  on  physical  chemistry,  and  while  the  results 
agree  well  with  the  old  method  of  calculating  counter-electromo- 
tive force,  the  modern  method  is  more  accurate,  as  it  considers  the 
variation  of  voltage  with  dilution. 

There  is  therefore  a  minimum  voltage  below  which  any  given 
metal  will  not  be  deposited,  so  that  theoretically,  if  all  metals  gave 
soluble  sulphates  or  nitrates,  we  could  apply  just  voltage  enough  to 
overcome  the  solution  tension  of  the  lowest  in  the  series  and  when 
that  metal  was  completely  deposited,  the  current  would  cease  to 
pass;  then  by  raising  the  current  to  just  above  the  intensity  re- 
quired for  the  next  metal,  that  could  be  deposited  and  so  on. 
This  is  evidently  not  possible  in  all  cases,  but  it  is  in  some.  If 
there  are  present  in  solution  copper  and  silver  as  nitrates  and  a 
current  of  one  volt  is  passed,  only  silver  is  thrown  out.  If  the 
sulphates  of  copper  and  zinc  are  in  solution  (containing  but  a  trace 
of  free  sulphuric  acid)  we  can  by  keeping  the  current  between  1.5 
and  2  volts  deposit  only  copper ;  while  by  raising  the  voltage  so 
as  to  exceed  the  solution  tension  of  the  zinc,  we  can  deposit  brass 
and  by  varying  the  voltage,  vary  the  percentage  composition  of 
the  alloy. 

To  return  to  the  copper,  we  can  prevent  some  metals  from  de- 
positing by  the  character  of  the  solution,  addition  of  acid,  etc., 
others  will  not  come  down  in  an  aqueous  solution  at  all,  others 
can  be  prevented  from  contaminating  the  copper  by  regulating  the 
voltage  so  that  the  counter-electromotive  force  of  copper  is  just 
exce.eded.  Practically  it  is  often  easier  to  remove  the  interfering 
element  than  to  regulate  the  voltage,  and  then,  when  there  is  no 
metal  present  which  will  come  down  at  a  higher  voltage,  we  need 
only  adjust  the  amperage  or  current  density  so  as  to  get  a  deposit 
suitable  for  weighing. 


90  QUANTITATIVE   ANALYSIS. 

ADDITIONAL  REFERENCES. 

"  The  Elements  of  Electrochemistry,"  by  LeBlanc,  translated  by 
W.  R.  Whitney  for  the  theory,  and  "  Quantitative  Chemical  An- 
alysis by  Electrolysis  "  by  Classen  for  other  methods. 

IODIDE  METHOD. 

In  an  acetic  acid  solution,  potassium  iodide  precipitates  cuprous 
iodide,  with  the  liberation  of  iodine,  according  to  the  reaction : 

2C4(CaH302)2  +  4KI  =  Cu2I2  +  I2  +  4KC2H302, 

or  one  atom  of  iodine  is  liberated  for  each  atom  of  copper  present 
in  the  cupric  condition. 

The  liberated  iodine  can  be  titrated  by  a  standard  solution  of 
sodium  thiosulphate,  using  starch  solution  as  indicator,  accord- 
ing to  the  reaction : 

2Na2S203  +  Jf  =  2NaI  +  Na2S4O6. 

Here  copper  acts  as  an  oxidizing  agent,  liberating  iodine,  which 
is  measured,  and  so  the  copper  is  determined  ;  a  method  of  indirect 
titration.  It  is  evidently  essential  to  the  success  of  this  method 
that  there  should  not  be  present  any  other  oxidizing  or  reducing 
agents,  for  the  first  would  liberate  iodine  and  cause  too  high  re- 
sults; the  latter  would  be  oxidized  by  the  iodine  liberated  and 
cause  too  low  results. 

The  indicator  is  a  solution  of  starch  which  gives  an  intense  blue 
color  to  the  solution  in  the  presence  of  free  iodine.  The  end  point 
is  the  discharge  of  this  blue  color  and  is  extremely  delicate  when 
the  proper  conditions  have  been  observed.  The  starch  solution  is 
made  by  mixing  about  one  gram  of  pure  starch  to  a  thin  paste  with 
cold  water  and  then  pouring  it  into  about  200  c.c.  of  boiling  water 
and  boiling  for  several  minutes.  It  should  be  allowed  to  cool  and 
only  the  clear  solution  used.  This  solution  does  not  keep  well ; 
moulds  grow  in  it  which  split  up  the  starch  giving  dextrins  and 
other  carbohydrates,  some  of  which  give  reddish  colors  with  iodine. 
To  guard  against  this  a  preservative  such  as  zinc  chloride  or  carbon 
bisulphide  may  be  added. 

A  standard  solution  of  sodium  thiosulphate  is  made  by  dissojving 
19.6  grams  of  the  crystallized  salt,  Na2S2O3.  5H2O,  in  water  and 
diluting  to  one  liter.  Each  c.c.  will  be  equivalent  to  about  5  milli- 
grams of  copper.  Standardize  as  follows  :  Weigh  out  two  or  three 


THE   DETERMINATION    OF    COPPER.  91 

portions  of  pure  bright  copper  foil  of  100-150  milligrams  each, 
taking  different  weights,  as  this  ensures  a  really  independent  de- 
termination and  saves  the  time  required  to  weigh  out  an  exact 
amount.  Dissolve  the  copper  in  small  beakers  in  about  10  c.c.  or 
less  of  nitric  acid  1.2  sp.  gr.,  evaporate  until  all  red  fumes  and  all 
excess  of  nitric  acid  are  expelled,  best  on  a  steam  bath ;  redissolve 
the  copper  nitrate  in  a  little  water,  add  a  few  drops  of  sodium 
hydroxide,  which  should  give  a  slight  precipitate  of  cupric  hy- 
droxide, dissolve  this  in  a  few  c.c.  of  acetic  acid,  allow  to  cool  and 
dilute  with  cold  water  to  about  50  c.c. 

Next  add  three  grams  of  potassium  iodide  crystals  (or  in  solu- 
tion), stirring  until  they  have  dissolved.  The  solution  now  con- 
tains a  precipitate  of  almost  white  cuprous  iodide  and  is  colored 
brown  by  the  liberated  iodine.  Run  in  the  sodium  thiosulphate 
solution  from  a  burette  until  the  brown  color  is  very  faint,  a  light 
straw  color,  then  add  about  5  c.c.  of  the  clear  starch  solution  and 
continue  the  titration  until  the  blue  is  discharged.  Near  the  end 
the  sodium  thiosulphate  must  be  run  in  drop  by  drop  and  the  solu- 
tion stirred  thoroughly.  Titrate  the  other  portions  and  calculate 
the  value  of  the  solution  in  terms  of  copper.  The  standards  should 
not  differ  by  more  than  one  in  the  fifth  decimal  place  (third  signifi- 
cant figure). 

The  blue  color  will  return  after  a  time  due  to  oxidation  by  the 
air.  If  the  solution  remains  colorless  for  two  minutes  the  end  has 
been  reached  and  the  titration  is  satisfactory.  If  the  blue  reap- 
pears almost  immediately  there  is  probably  some  oxidizing  agent 
present  and  if  this  continues  after  the  addition .  of  a  couple  more 
drops  of  thiosulphate  solution  the  determination  is  useless. 

After  the  potassium  iodide  has  been  added  the  solution  must  be 
kept  cold  to  avoid  loss  of  iodine  and  titrated  without  delay  to 
avoid  oxidation  by  the  air.  As  large  amounts  of  sodium  acetate 
interfere  with  the  end  point,  by  causing  a  return  of  the  blue  color, 
care  should  be  taken  to  add  only  a  few  drops  of  sodium  hydroxide 
solution  (not  carbonate)  in  neutralizing  the  nitric  acid. 

Assay.  —  To  the  sulphate  solution  of  the  ore  or  matte  add  two 
pieces  of  sheet  aluminum,  one  sixteenth  inch  thick  and  one  and 
one  half  inches  square,  whose  corners  are  bent  so  that  the  two 
pieces  only  touch  at  the  points  and  so  present  a  large  surface, 
then  about  5  c.c.  of  strong  sulphuric  acid.  Heat  to  boiling,  cov- 
ered to  prevent  spattering,  until  all  the  copper  is  precipitated.  Pour 


92  QUANTITATIVE   ANALYSIS. 

the  solution  and  that  portion  of  the  copper  which  does  not  adhere 
to  the  aluminum  foil  into  a  clean  beaker  and  allow  the  copper  to 
settle  ;  then  decant  through  a  filter,  wash  the  aluminum  foil  coated 
with  copper,  with  water  and  the  copper  in  the  second  beaker,  pour 
the  washings  through  the  same  filter ;  remove  the  vessel  contain- 
ing the  filtrate  and  washings  and  substitute  the  other  beaker  con- 
taining the  non-adherent  copper  ;  to  the  beaker  containing  the 
aluminum  foil  add  $—6  c.c.  of  nitric  acid  1.2  sp.  gr.  and  warm  till 
all  the  copper  has  dissolved,  then  pour  the  acid  copper  nitrate  solu- 
tion through  the  filter  into  the  beaker  below,  which  contains  the 
rest  of  the  copper  and  heat  till  all  the  copper  has  dissolved. 

If  the  precipitated  copper  is  red  in  color  and  evidently  pure,  the 
washings  of  the  beakers  and  filter  can  be  added  at  once  and  the 
excess  of  nitric  acid  expelled  and  the  copper  titrated  exactly  as  in 
standardizing.  If  the  copper  is  dark,  before  diluting  with  the 
washings  add  half  a  gram  of  potassium  or  sodium  chlorate  and 
boil  to  oxidize  any  arsenic  which  may  be  deposited  with  the  cop- 
per, then  add  the  washings  and  evaporate  as  usual.  When  anti- 
mony is  present  it  will  be  oxidized  by  the  nitric  acid  and  be  almost 
all  filtered  out ;  the  traces  which  dissolve  must  be  oxidized  like  the 
arsenic.  It  is  of  the  utmost  importance  that  all  the  chlorate  is  de- 
composed and  the  chlorine  and  oxides  of  chlorine  boiled  out,  as 
these  would  liberate  iodine  later  on. 

Bismuth  will  be  deposited  with  the  copper  by  the  aluminum,  it 
will  dissolve  in  nitric  acid  and  unless  thrown  out  as  a  basic  salt  when 
the  copper  nitrate  is  dissolved  in  water,  will  precipitate  as  a  brown 
iodide,  Bilg.  As  this  is  not  attended  by  any  liberation  of  iodine 
it  will  not  affect  the  results,  but  as  this  iodide  is  somewhat  soluble 
in  potassium  iodide  a  brown-colored  solution  is  produced,  which 
may  look  like  liberated  iodine, and  so  too  much  thiosulphate  solu- 
tion may  be  run  in  before  the  starch  solution  is  added. 

In  titrating  some  ores  the  end  point  may  not  be  exactly  the  same 
as  with  pure  copper,  due  to  impurities,  such  as  bismuth,  lead,  etc., 
which  give  a  greenish  solution  after  the  starch  is  added,  so  that  the 
change  is  not  from  blue  to  white,  but  from  a  dirty  green  to  a  yel- 
lowish white. 

The  amount  of  potassium  iodide  has  been  given  as  three  grams ; 
this  quantity  is  required  for  the  reaction  and  the  excess  necessary 
to  hold  the  liberated  iodine  in  solution.  More  does  no  harm,  but 
as  the  reagent  is  expensive,  it  should  be  used  sparingly.  The  end 


THE   DETERMINATION    OF    COPPER.  93 

point  is  so  sharp  that  slight  variations  of  the  volume  or  of  the 
amount  of  copper  present  have  no  effect.  Ferric  salts  cannot  be 
present,  as  they  liberate  iodine;  in  the  method  described  they  are 
reduced  to  the  ferrous  condition  when  the  copper  is  precipitated 
by  aluminum  and  are  thrown  away  in  the  filtrate.  If  sodium  car- 
bonate is  used  instead  of  hydroxide  in  neutralizing  the  copper  nitrate 
solution  some  copper  remains  in  solution  as  bicarbonate.  Then, 
when  the  potassium  iodide  is  added,  iodine  and  carbon  dioxide 
are  liberated  together,  and  some  iodine  is  lost  by  being  carried  out 
with  the  carbon  dioxide. 

It  has  been  proposed  recently  by  Low  to  neutralize  here  with 
ammonia  and  then  to  acidify  by  acetic  acid  as  described :  also  to 
oxidize  any  arsenic  or  antimony  present  to  the  pentad  condition 
by  bromine  instead  of  chlorate.  For  further  information  on 
this  method  see:  Low,  y.  Am.  Chem.  Soc.,  18,  458  and  24,  1082, 
1902.  Beringer's  "Assaying,"  p.  160. 

POTASSIUM  CYANIDE  METHOD. 

This  method  is  very  largely  used,  as  it  is  more  rapid  and  less 
expensive  than  the  iodide  method.  It  depends  on  the  conversion 
of  the  intensely  blue  Cu(NH3)4  ion  into  a  colorless  Cu(CN)2  ion, 
or  practically  the  measurement  of  the  amount  of  potassium  cyanide 
solution  necessary  to  decolorize  the  ammoniacal  solution  of  copper 
nitrate  or  sulphate. 

The  reaction  for  the  sulphate  is  given  by  Treadvvell  as  follows : 

2Cu(NH3)4S04,H20  +  4KCN  =  2Cu(CN)f  +  8NH3  +  2K2SO4, 

then  the  2Cu(CN)2  breaks  up,  giving  Cu2(CN)  and  (CN)2,  and,  if 
sufficient  potassium  cyanide  is  present,  forms  K4Cu2(CNT)6,  while 
the  (CN)2  reacts  on  the  excess  of  ammonia,  like  Cl  on  KOH,  giving 
NHCN  and  NH4CNO.  So  the  complete  reaction  is, 

2Cu(NH3)4  SO4,H2O  +  8KCN  =  K4Cu(CN)6  +  NH4CN 
+  NH4CNO  +  6NH3  +  2K2SO4. 

This  is  not  advanced  as  a  perfect  explanation  of  what  takes 
place,  but  to  show  how  complex  the  simplest  form  of  the  reaction 
is.  Then  if  we  begin  to  consider  the  influence  of  other  salts 
present  and  the  easy  conversion  of  ammonium  cyanate  into  urea, 
a  large  field  of  possible  organic  compounds  is  opened  ;  so  it  is  evi- 


94  QUANTITATIVE   ANALYSIS. 

dent  that  the  reaction  must  be  carried  out  under  identical  condi- 
tions in  order  to  obtain  accurate  results.  The  following  facts 
also  emphasize  this : 

1.  Increase  of  temperature  decreases  the  intensity  of  the  blue 
color. 

2.  A  large  excess  of  free  ammonia  tends  to  vary  the  color  and 
give  low  results. 

3.  Ammonium  sulphate  gives  low  results. 

4.  Hydroxides,  bicarbonates,   sulphites  and   nitrites  affect   the 
results. 

5.  Salts  of  silver,  zinc,  nickel,  etc.,  which  react  with  potassium 
cyanide  must  be  absent. 

6.  Ferric  or  manganese  hydroxides  should  not  be  present,  as 
they  hold  copper  and  mar  the  end  point. 

The  titration  must  therefore  be  made  in  the  absence  of  iron, 
manganese,  zinc,  nickel  or  silver  salts,  best  without  ammonia  salts, 
at  the  same  temperature  (the  lower  the  sharper  the  end  point), 
with  the  same  excess  of  ammonia,  with  the  same  volume  at 
the  end,  and  with  approximately  the  same  amount  of  copper 
present. 

Make  up  a  solution  containing  22  grams  of  pure  potassium 
Cyanide  per  liter.  Weigh  out  two  or  three  portions  of  pure  copper 
about  150  milligrams  each;  dissolve  them  in  nitric  acid, in  a  beaker 
capable  of  holding  200  c.c.  easily,  with  a  mark  at  150  c.c. ;  boil 
out  the  oxides  of  nitrogen ;  dilute  with  cold  water  to  about  80  c.c. ; 
neutralize  with  dilute  caustic  soda  solution  till  a  faint  permanent 
precipitate  forms ;  then  add  6  c.c.  of  strong  ammonia  (0.9  sp.  gr.) 
and  run  in  the  potassium  cyanide  solution  till  the  blue  color  is  very 
faint;  dilute  to  the  mark  (150  c.c.)  and  continue  the  titration  until 
the  solution  is  colorless. 

To  apply  the  method  to  ores,  etc.,  follow  the  directions  given  for 
the  iodide  method  until  the  copper  is  precipitated  on  aluminum 
foil,  dissolve  this  in  nitric  acid  and  proceed  as  in  standardizing. 

The  method  is  very  accurate  after  a  little  experience  with  the 
end  point,  and  its  most  important  feature  is  the  necessity  of  abso- 
lute uniformity  in  the  conditions  of  titration.  Should  great  rapidity 
be  required  at  the  expense  of  accuracy,  the  ore  can  be  dissolved 
in  nitric  acid,  an  excess  of  ammonia  added,  then  titrated  to  a  faint 
blue,  the  residue  ferric  hydroxide,  etc.,  filtered  out,  and  the  titration 
finished  on  the  clear  filtrate. 


THE   DETERMINATION    OF    COPPER.  95 

The  cyanide  solution  keeps  best  in  the  dark,  but  as  it  is  con- 
stantly losing  hydrocyanic  acid  it  requires  frequent  standardizing. 

For  further  information  see:  Beringer's  "Assaying,"  p.  154, 
and  H.  H.  Miller,  Irans.  A.  I.  M.  £.,  Nov.,  1901. 

THIOCYANATE  METHOD. 

This  method  has  many  modifications  and  is  only  recommended 
for  low  grade,  impure  ores  or  tailings  containing  less  than  three 
per  cent,  of  copper  and  particularly  when  the  impurities  are  arsenic 
and  antimony.  What  follows  is  taken  largely  from  an  article  by 
Guess,*  and  the  thesis  of  Lindeman,  Columbia  University,  1903. 

The  essential  features  of  the  method  are  as  follows,  the  prelimi- 
nary treatment  being  as  already  given  :  The  filtrate  containing  sul- 
phates is  neutralized  by  ammonia  and  then  rendered  acid  by  either 
hydrochloric  or  sulphuric  acid  (i  per  cent,  of  either  is  sufficient 
acidity),  next  a  slight  excess  of  sulphurous  acid  is  added  and  the 
solution  heated,  then  a  decided  excess  of  potassium  thiocyanate  f  is 
added  and  the  solution  stirred  vigorously  for  a  couple  of  minutes 
on  the  water-bath  ;  filtered  immediately  and  washed  with  hot  acid- 
ulated water  several  times.  The  precipitate  is  treated  in  the  funnel 
with  a  hot  10  per  cent,  solution  of  sodium  hydroxide,  giving  sod- 
ium thiocyanate,  which  is  obtained  in  a  clean  beaker,  and  cuprous 
hydroxide  which  is  left  on  the  paper.  This  is  washed  by  hot 
water.  The  alkaline  filtrate  is  acidified  with  dilute  sulphuric  acid 
and  the  free  hydrothiocyanic  acid  is  titrated  (warm)  by  potas- 
sium permanganate,  according  to  the  reaction,  loHSCN  -f  12 
KMnO4  4-  8H2SO4  =  6K2SO,  +  i2MnSO4  +  loHCN  +  8H2O. 

The  theoretical  factor  for  changing  the  iron  standard  to  the  cop- 
per standard  is  0.1920,  but  it  is  safer  to  standardize  against  cop- 
per on  account  of  the  slight  solubility  of  the  cuprous  hydroxide  in 
caustic  alkali.  The  results  so  obtained  agreed  with  a  factor  of 
0.1892.  Of  the  metals  likely  to  be  present  silver  and  possibly 
bismuth  are  the  only  ones  which  give  insoluble  thiocyanates  under 
the  conditions  given.  The  silver  would  not  interfere,  for  if  not 
thrown  out  as  chloride,  the  silver  thiocyanide  would  be  left  with 
the  cuprous  hydroxide  as  it  is  not  easily  decomposed  by  alkali. 
The  bismuth  thiocyanate  is  soluble  in  acids  and  will  usually  be 
held  in  solution  unless  much  is  present.  It  is,  however,  precipi- 

* J.  American  Chem.  Soc.,  24,  708,  1902. 
f  Often  called  sulphocyanide. 


96  QUANTITATIVE   ANALYSIS. 

tated  as  metallic  bismuth  if  a  large  excess  of  sulphurous  acid  is 
used  in  effecting  the  reduction  of  the  copper. 

The  weak  point  of  the  method  is  the  precipitation  of  the 
cuprous  thiocyanate,  which  requires  careful  regulation  of  the 
acidity,  especially  when  bismuth  is  present.  The  advantages  are 
the  large  quantity  of  permanganate  used  for  small  amounts  of 
copper  and  the  non-interference  of  arsenic  and  antimony. 

The  precipitation  of  copper  as  thiocyanate  is  used  in  alloys 
such  as  german  silver,  and  to  separate  the  bulk  of  the  copper  from 
the  impurities  in  the  analysis  of  pig  copper. 

ADDITIONAL  REFERENCES. 

VAN  NAME.     American  J.  Science,  163,  138-144. 
PARR,  J.     Am.  Chem.  Soc.,  22,  685,  1900. 
MEADE.     J.  Am.  Chem.  Soc.,  20,  610,  i 


THE    DETERMINATION    OF    LEAD.  97 

CHAPTER  XII. 

The  Determination  of  Lead  in  Ores. 

The  well-known  inaccuracy  of  the  fire  assay  for  lead  has  rendered 
more  important  the  volumetric  methods  for  its  determination. 
The  basis  for  the  sale  of  ores  is  now,  in  many  cases,  the  percentage 
catually  present,  as  shown  by  wet  methods,  minus  two  per  cent., 
instead  of  the  fire  assay  results.* 

The  methods  to  be  described  are:  First,  the  gravimetric,  weigh- 
ing as  sulphate ;  second,  the  ferrocyanide ;  third,  the  molybdate. 
While  there  are  many  other  excellent  methods,  notably  Koenig's 
alkalimetric,  and  the  various  modifications  of  the  chromate,  the 
three  described  are  sufficient. 

GRAVIMETRIC  AS  LEAD  SULPHATE. 

Treat  from  0.5  to  I  gram  of  the  very  finely  ground  ore,  depend- 
ing on  the  amount  of  lead  present,  with  15-20  c.c.  of  concentrated 
nitric  acid  and  a  few  drops  of  concentrated  hydrochloric  acid  in 
a  small  covered  casserole  or  Erlenmeyer  flask ;  boiling  until  no 
further  solution  takes  place  and  the  sulphur  (if  the  ore  is  a  sulphide) 
is  completely  oxidized,  adding  more  acids  if  necessary  to  complete 
the  decomposition.  Allow  to  cool  slightly  and  add  about  10  c.c. 
of  sulphuric  acid  1.41  sp.  gr.  (i  part  concentrated  acid  to  I  of 
water)  and  evaporate  to  copious,  dense  fumes  of  sulphur  trioxide. 
All  the  common  ores  of  lead  will  be  decomposed  by  this  treat- 
ment, which  is  carried  out  as  already  described  under  copper. 
The  addition  of  a  little  hydrochloric  acid  is  not  always  required, 
but  usually  aids  in  the  solution  of  the  lead.  The  evaporation 
should  be  nearly  to  dryness  so  as  to  ensure  the  complete  conversion 
of  lead  to  sulphate  and  also  to  prevent  there  being  present  too  great 
an  excess  of  sulphuric  acid  after  dilution,  more  than  I— 2  per  cent. 

Allow  the  lead  sulphate,  etc.,  to  cool  and  add  cautiously  about 
100  c.c.  of  distilled  water  and  boil  for  several  minutes  to  dissolve 
the  ferric  sulphate,  etc.,  allow  to  cool  and  add  about  15  c.c.  of 
strong  alcohol,  stir  well,  allow  to  settle  and  decant  through  a  small 
filter,  leaving  as  much  as  possible  of  the  insoluble  sulphates  and 
the  silicious  residue  in  the  casserole  or  flask.  Wash  the  residue 

*  See  lies,  SCHOOL  OF  MINES  QUARTERLY,  Vol.  XV.,  p.  336,  1894. 


98  QUANTITATIVE    ANALYSIS. 

by  decantation  thoroughly  with  water  containing  I  per  cent,  sul- 
phuric acid  and  10  per  cent,  alcohol.  Pouring  the  washings  through 
the  filter,  and  wash  finally  with  alcohol  alone  to  remove  the  sulphuric 
acid.  Place  a  clean  beaker  under  the  funnel,  dissolve  the  lead  sul- 
phate from  the  residue  in  a  strong  hot  solution  of  ammonium 
acetate,  slightly  acid  with  acetic  acid ;  pour  this  solution  through 
the  filter  into  a  clean  beaker.  Repeat  this  treatment  until  all  the 
lead  sulphate  has  dissolved  ;  then  wash  the  residue  onto  the  filter 
and  wash  it  finally  with  hot  water.  Most  of  the  trouble  in  the  de- 
termination of  lead  occurs  just  at  this  point;  lead  sulphate  when 
free  from  other  insoluble  sulphates  and  freshly  precipitated  dis- 
solves readily  in  hot  ammonium  acetate,  but  when  ignited  or  if 
contaminated  by  barium,  strontium  or  calcium  sulphates,  boiling 
for  half  an  hour  with  a  liberal  excess  of  ammonium  acetate  is  abso- 
lutely necessary  for  its  complete  solution.  The  ammonium  acetate 
is  best  made  by  neutralizing  acetic  acid  with  ammonia  as  the 
crystallized  salt  is  an  expensive  reagent  and  has  to  be  used  in 
large  quantities.  On  solution  Pb(C1H8Og)s  and  (NH,)2Pb(SO4)2  are 
formed.  The  filtrate  is  acidified  with  dilute  sulphuric  acid,  which 
reprecipitates  the  lead  sulphate,  alcohol  is  added  as  before  (about 
10  per  cent.)  and  the  precipitate  filtered  and  washed;  first  with  I 
per  cent,  sulphuric  acid  and  10  per  cent,  alcohol  and  finally  with 
strong  alcohol  alone,  either  ethyl  or  methyl. 

The  ignition  of  the  lead  sulphate,  when  filtered  on  paper,  gives 
considerable  trouble  and  often  inaccurate  results  because  the  car- 
bon of  the  paper  causes  reduction  to  sulphide  and  sometimes  to 
metallic  lead,  which  requires  reconversion,  by  nitric  and  sulphuric 
acids,  to  lead  sulphate,  often  accompanied  by  mechanical  loss. 
This  difficulty  can  be  overcome  by  using  a  Gooch  crucible  with 
asbestos  alone,  or  as  follows  :  Cut  out  two  pieces  of  "  acid- washed" 
filter  paper  so  as  to  fit  the  bottom  of  the  crucible  accurately  (using 
a  5 -cent  piece)  and  place  them  on  the  bottom  of  the  crucible;  then 
on  top  of  these  a  thin  layer  of  asbestos  which  has  been  washed 
with  dilute  sulphuric  acid,  making  a  layer  of  about  T3^-  of  an  inch ; 
then,  while  still  wet,  suck  this  down  by  a  strong  suction  as  tightly 
as  possible  and  dry  in  an  oven  to  constant  weight  at  1 10°  C.  After 
weighing  moisten  the  filter  and  then  pour  in  the  solution  contain- 
ing the  lead  sulphate,  using  a  very  gentle  suction  at  the  beginning; 
wash  as  described,  dry  again  at  110°  C.  and  the  increased  weight 
is  lead  sulphate. 


THE   DETERMINATION    OF   LEAD.  99 

This  method  has  been  thoroughly  tested  and  will  yield  results 
(when  properly  carried  out)  which  are  accurate  to  within  a  few 
hundredths  of  a  per  cent.  When  such  accurate  work  is  not  required 
the  alcohol  may  be  omitted,  but  the  use  of  the  Gooch  crucible  is 
strongly  recommended  when  the  necessary  suction  can  be  obtained. 

Lead  sulphate  is  slightly  soluble  in  water  and  quite  soluble  in 
concentrated  sulphuric  acid ;  it  is  almost  insoluble  in  a  I  per  cent- 
solution  of  sulphuric  acid  and  insoluble  in  alcohol.  Besides  being 
soluble  in  ammonium  acetate  it  is  soluble  in  ammonium  chloride 
and  other  ammonium  salts.  Boiling  with  alkali  carbonates  con- 
verts it  to  carbonate,  which  can  then  be  readily  dissolved  in  acids. 
Koenig  dissolves  the  lead  carbonate  in  standard  nitric  acid  and 
then  by  titrating  back  with  a  standard  solution  of  caustic  soda, 
using  methyl  orange  as  an  indicator,  determines  the  quantity  of 
acid  required  to  dissolve  the  lead  and  so  finds  the  lead  present. 
This  method  has  a  great  advantage  over  the  other  volumetric 
methods  in  the  end  point,  which  is  sharp  and  satisfactory,  while 
the  others  are  spot  tests  and  an  allowance  for  the  excess  required 
must  be  subtracted,  as  in  the  zinc  titration  by  potassium  ferrocya- 
nide.  Lead  sulphate  is  not  volatilized  if  present  when  silica  is 
driven  off  by  hydrofluoric  and  sulphuric  acids.* 

In  some  cases  it  is  preferable  to  precipitate  the  lead  as  sulphide 
and  subsequently  convert  it  to  sulphate  by  strong  nitric  acid.  It 
should  be  borne  in  mind  that  lead  sulphide  is  the  most  soluble  of 
the  fifth-  and  sixth-group  sulphides  in  hydrochloric  acid,  so  that 
less  than  2  c.c.  of  concentrated  hydrochloric  acid  should  be  present 
in  each  100  c.c.  of  solution.  It  can  also  be  precipitated  from  a 
neutral  or  alkaline  solution,  or  one  slightly  acid  with  nitric  acid. 
This  separation  is  often  necessary  with  alloys  containing  antimony, 
tin,  etc.,  where  the  sixth-group  metal  is  subsequently  removed  by 
digesting  with  fixed  alkali  sulphide. 

FERROCYANIDE  METHOD. 

This  method  is  the  same  as  the  gravimetric  up  to  the  point 
where  the  lead  sulphate  and  insoluble  residue  has  been  washed  free 
from  sulphuric  acid.  Add  to  the  residue  in  a  flask  or  casserole  at 
least  15  c.c.  of  a  solution  of  commercial  ammonium  carbonate,  sat- 
urated in  the  cold ;  heat  to  boiling,  then  allow  to  cool,  and  filter 
through  the  filter  already  used  to  retain  any  lead  sulphate  from 

*Meade,/.  Am.  Chem.  Sec.,  Vol.  XIX..,  p.  37,  1897. 


ioo  QUANTITATIVE   ANALYSIS. 

washing  the  lead  sulphate  and  residue.  Wash  the  flask  and  pre- 
cipitate till  the  washings  show  no  alkaline  reaction.  Place  in  the 
flask  10  c.c.  of  50  per  cent,  acetic  acid  and  about  20  c.c.  of  water 
and  boil  till  the  lead  carbonate  has  dissolved  completely ;  dilute  to 
nearly  IOO  c.c.,  warm  to  60°  C,  and  titrate  by  potassium  ferrocy- 
anide,  using  uranium  nitrate  as  an  indicator,  as  with  zinc. 

As  in  the  zinc  titration,  uniformity  in  the  conditions  for  titration 
are  essential  to  correct  results.  The  same  standard  solution  can  be 
used,  or  better,  one  half  the  strength,  about  10  grams  of  crystallized 
potassium  ferrocyanide  per  liter.  With  such  a  solution  the  allow- 
ance for  the  indicator  should  be  about  o.S  c.c. ;  with  the  stronger 
solution,  of  course,  it  is  less.  This  allowance  is  a  matter  of  indi- 
vidual eyesight  and  should  be  determined  on  a  blank  test  made  up 
of  ioo  c.c.  of  water  and  10  c.c.  of  50  per  cent,  acetic  acid  at  a 
temperature  of  60°  C. 

The  standard  is  obtained  by  treating  portions  of  pure  dry  lead 
sulphate  with  ammonium  carbonate,  dissolving  the  lead  carbonate 
in  acetic  acid  and  titrating  under  the  conditions  given. 

The  formula  of  the  precipitate  is  nearly  Pb2Fe  (CN)6.  It  does 
not  vary  as  greatly  with  changed  conditions  as  the  zinc  ferrocyanide 
does,  but  as  it  is  much  more  soluble  equal  care  must  be  exercised 
in  obtaining  just  the  conditions  given.  The  objectionable  fea- 
ture is  the  end  point.  Many  other  indicators  have  been  tried,  but 
nothing  better  than  uranium  salts  has  been  found.  The  good  fea- 
ture of  the  method,  which  is,  in  fact,  the  reason  for  giving  it  a 
slight  preference  over  all  the  others  is  that  the  impurities  likely  to 
be  present  are  almost  without  effect.  Antimony  even  if  present  to 
the  extent  of  0.200  gram  is  absolutely  without  effect.  Bismuth  gives 
results  slightly  low,  but  as  0.360  gram  only  lowers  the  amount  of 
I  per  cent,  ferrocyanide  used  by  0.6  c.c.  it  will  not  affect  results  when 
present  in  small  quantities.  Calcium  and  strontium  are  without 
effect.  Barium  gives  slightly  low  results.  These  statements  are 
based  on  a  series  of  experiments  carried  out  exactly  as  the  method 
is  described  here,  the  low  results  are  not  to  be  attributed  to  the 
titration  but  to  the  barium  and  bismuth  interfering  with  the  con- 
version of  lead  sulphate  to  carbonate,  for  this  reason,  in  some  cases, 
the  amount  of  ammonium  carbonate  solution  should  be  increased 
considerably,  even  up  to  50  c.c.,  and  also  the  time  of  heating. 

The  other  metals  which  give  insoluble  ferrocyanides  do  not  give 
insoluble  sulphates  or  basic  salts,  so  they  pass  into  the  filtrate  when 
the  lead  sulphate  and  residue  are  filtered. 


THE   DETERMINATION    OF   LEAD.  101 

MOLYBDATE    METHOD. 

This  is  based  on  the  precipitation  of  lead  as  PbMoO4  by  a  standard 
solution  of  ammonium  molybdate  in  a  hot  solution  slightly  acid 
with  acetic  acid.*  The  end  point  is  a  spot  test  with  tannin  solu- 
tion which  turns  yellow  when  the  molybdate  is  in  excess. 

The  standard  ammonium  molybdate  is  made  by  dissolving  9 
grams  of  the  pure  salt  in  water  and  diluting  to  one  liter;  if  the 
solution  is  not  clear,  add  a  few  drops  of  ammonia.  It  is  standard- 
ized by  weighing  out  several  portions  of  dry  lead  sulphate  ;  dis- 
solving them  in  hot  ammonium  acetate ;  adding  2-3  c.c.  of  acetic 
acid  and  titrating  at  about  90°  C.  till  a  drop  of  the  clear  solution 
gives  a  slight  but  distinct  yellow  color  with  a  drop  of  a  freshly  pre- 
pared tannin  solution,  which  contains  about  I  gram  to  300  c.c.  of 
water.  The  most  important  point  is  to  titrate  hot.  If  the  solution 
has  become  cool  on  account  of  slow  work  in  titration,  it  should  be 
heated  again  so  that  it  is  hot  when  the  titration  is  finished.  The 
solution  should  be  decidedly  acid  with  acetic  acid.  Here  and  also 
in  the  preceding  method  the  plan  given  under  zinc  of  dividing  the 
solution  roughly  in  half  for  titration  can  be  utilized. 

As  an  allowance  must  be  made  for  the  excess  necessary  to 
affect  the  indicator,  uniformity  in  volume  is  essential ;  200  c.c.  is 
recommended.  With  this  volume  and  the  conditions  given  the 
allowance  should  not  exceed  O.8  c.c.  Many  attempts  have  been 
made  to  obtain  a  more  satisfactory  end  point  for  this  method  but 
so  far  in  vain.  The  most  satisfactory  substitute  has  been  devised 
by  J.  L.  Danziger.  Crystals  of  stannous  chloride  are  dissolved 
in  acetic  acid  till  a  saturated  solution  is  formed;  this  is  then  satu- 
rated with  ammonium  thiocyanate.  The  solution  so  obtained 
gives  a  pink  color  with  ammonium  molybdate  and  is  about  as  deli- 
cate as  the  tannin  reaction. 

To  apply  this  method  to  an  ore,  follow  the  gravimetric  method 
till  the  lead  sulphate  is  dissolved  in  ammonium  acetate,  acidify 
with  2-3  c.c.  of  acetic  acid,  dilute  to  200  c.c.,  heat  to  boiling  and 
titrate  as  in  standardizing. 

Interferences. — Antimony  and  bismuth  are  without  effect.  Barium 
gives  very  low  results:  strontium  low  results:  calcium  very 
slightly  low  results,  but  not  enough  to  affect  ordinary  work.  As 
in  the  ferrocyanide  method  the  action  of  these  alkaline  earth  sul- 
phates is  to  impede  the  solution  of  the  lead,  and  the  difficulty  can 

*  H.  H.  Alexander,  Engineering  and  Mining  Journal,  April,  1893,  p.  298. 


102  QUANTITATIVE   ANALYSIS. 

be  entirely  overcome  by  thoroughly  washing  the  lead  sulphate 
and  then  boiling  it  repeatedly  with  sufficient  ammonium  acetate. 
For  comparative  results  on  these  and  other  methods  see  Bull, 
SCHOOL  OF  MINES  QUARTERLY,  Vol.  XXIII.,  pp.  348-366,  also  Z. 
fur  analytische  Chemie,  Vol.  41,  pp.  653-674,  1902. 


THE    DETERMINATION    OF    ANTIMONY.         103 


CHAPTER  XIII. 

The  Determination  of  Antimony  in  Ores. 

On  account  of  the  great  inaccuracy  of  the  fire  assay  for  antimony 
it  has  been  abandoned  and  its  place  taken  by  a  "  wet  assay." 
Before  describing  these  methods  a  short  description  of  the  gravi- 
metric determination  will  be  given  and  a  few  of  the  more  important 
separations  of  antimony. 

The  important  ores  of  antimony  are  stibnite  Sb2S3,  cervantite 
Sb2O4,  produced  by  the  oxidation  of  the  sulphide,  and  mixtures  of 
the  two  usually  containing  more  sulphide  than  oxide.  As  stibnite 
is  soluble  in  hydrochloric  acid  containing  a  few  drops  of  nitric, 
and  cervantite  is  practically  insoluble,  we  have  three  classes  of 
ores  ;  first,  the  soluble,  stibnite  and  also  the  rarer  oxide,  senarmon- 
tite,  Sb2O3 ;  second,  the  insoluble ;  third,  the  partially  soluble. 
They  will  be  discussed  in  this  order.  The  following  method  is 
taken  largely  from  an  article  by  Brown,  Journal  American  Chemical 
Society,  21,  780,  1899. 

GRAVIMETRIC  METHOD. 

Soluble  Ores.  —  One  gram  of  the  finely  ground  ore  is  placed  in  a 
small  beaker,  25  c.c.  of  concentrated  hydrochloric  acid  added,  cov- 
ered with  a  watch  glass  and  boiled  until  the  ore  is  apparently  decom- 
posed, which  reduces  the  hydrochloric  acid  to  about  15  c.c.;  about  2 
grams  of  tartaric  acid  are  added  and  when  dissolved  5  or  6  drops 
of  concentrated  nitric  acid  and  the  boiling  continued  for  several 
minutes.  The  nitric  acid  causes  a  violent  reaction,  accompanied 
by  a  more  complete  decomposition  of  the  ore.  The  solution  is 
allowed  to  cool,  diluted  slightly,  the  residue  filtered,  and  washed 
with  water.  The  residue  should  be  tested  for  antimony,  unless 
the  ore  is  known  to  be  completely  soluble.  The  filtrate  is  diluted 
to  about  250  c.c.  and  the  antimony  is  precipitated  as  sulphide  by 
a  stream  of  hydrogen  sulphide,  which  is  passed  through  for  an 
hour.  At  the  end  the  solution  should  be  warmed  to  insure  the 
conversion  of  any  basic  chloride  (formed  by  the  dilution)  to  sul- 
phide ;  after  standing  for  an  hour  to  allow  the  precipitate  to  collect 
and  settle,  it  is  filtered  and  washed  with  hydrogen  sulphide 
water.  There  may  be  present  in  the  ore,  arsenic  and  also  lead  and 


104  QUANTITATIVE   ANALYSIS. 

other  metals  of  the  fifth  group  ;  the  latter  will  be  evident  from  the 
dark  color  of  the  sulphide.  If  the  sulphide  is  impure,  warm  it  with 
a  strong  solution  of  ammonium  sulphide  (NHJ2S,  until  the  sul- 
phides of  arsenic  and  antimony  have  dissolved,  then  filter.  The 
residue  is  lead  sulphide,  etc. ;  in  it  the  lead  can  be  found  by  meth- 
ods already  given.  It  should  be  remembered  here  that  copper 
sulphide  is  slightly  soluble  in  ammonium  sulphide,  so  if  it  is  pres- 
ent sodium  or  potassium  sulphide  should  be  used. 

If  mercury  should  be  present  and  no  copper  use  ammonium 
sulphide  as  mercuric  sulphide  is  readily  soluble  in  the  fixed  alkali 
sulphides.  Tin  is  not  likely  to  be  present;  it  would  dissolve  with 
the  arsenic  and  antimony  readily  if  stannic  sulphide,  with  difficulty 
if  stannous  sulphide.  The  separation  of  antimony  from  tin  pre- 
sents considerable  difficulty.  See  the  standard  works  on  quanti- 
tative analysis  and  for  the  most  recent  descriptions  of  Clarke's 
method,  etc.,  Rossing,  Zeitschnft  fur  Analytische  Chemie,  41,  I, 
1902,  and  Henz,  Zeitschrift  fur  anorganische  Chemie,  37,  1-58, 
1903. 

The  separation  of  the  fifth  and  sixth  groups  is  also  incomplete 
by  the  ordinary  methods  when  there  are  present  mercury,  copper 
and  antimony,  as  sometimes  happens  with  tetrahedrite  (fahlerz). 
For  this  separation  see  Pretzfeld,y.  Am.  Chem.  Soc.,  Feb.,  1903. 

To  the  filtrate  containing  the  arsenic  and  antimony  as  sulpho- 
salts,  dilute  hydrochloric  acid  is  added  in  slight  excess,  then  the 
solution  is  diluted  to  ensure  complete  separation  of  the  antimony 
sulphide,  which  is  soluble  in  even  moderately  strong  hydrochloric 
acid,  and  the  mixture  of  sulphides  of  arsenic  and  antimony  and 
sulphur  is  filtered  on  balanced  filters,  washed  with  cold  water  and 
dried  at  110°  C.  for  two  hours  or  more  to  constant  weight.  This 
gives  the  total  weight  of  the  mixture.  It  is  removed  from  the 
paper,  ground  up  and  mixed  in  a  small  glass  mortar  and  an  exact 
weight,  about  0.5  gram,  is  weighed  off  in  a  platinum  or  porcelain 
boat.  This  is  placed  in  a  piece  of  hard  glass  combustion  tubing 
and  the  excess  of  sulphur,  over  that  required  to  form  Sb2S3  and  the 
sulphide  of  arsenic,  are  driven  off  by  heating  in  a  current  of  carbon 
dioxide  for  12-15  minutes.  A  steady  stream  of  carbon  dioxide 
should  be  passed  through  the  tube  to  displace  the  air  before  the 
heating  is  begun,  so  as  to  prevent  oxidation ;  the  heating  should 
be  gradual  and  the  final  temperature  about  250°  C.,  considerably 
below  a  dull  red  heat. 


THE   DETERMINATION    OF   ANTIMONY.        105 

From  the  weight  of  the  residue  of  black  antimonous  sulphide, 
the  total  antimony  in  the  mixture  of  sulphides  and  sulphur  is  cal- 
culated and  so  the  antimony  in  the  ore.  Should  it  be  impossible 
to  carry  out  this  method,  which  is  the  best,  the  mixture  of  sulphide, 
or  a  portion  of  it,  can  be  converted  to  oxide,  Sb2O4  by  treating 
repeatedly  with  strong  nitric  acid.  This  method  is  not  recom- 
mended as  it  is  almost  always  attended  by  mechanical  loss,  but  if 
nothing  better  can  be  done,  carry  it  out  as  follows :  Transfer  as 
much  as  possible  of  the  dried  precipitate  to  a  porcelain  crucible, 
dissolve  what  adheres  to  the  filter  in  freshly  made  ammonium  sul- 
phide, using  as  little  as  possible,  and  add  the  solution  to  the  pre- 
cipitate in  the  crucible;  evaporate  on  a  water-bath,  add  fuming 
nitric  acid  and  allow  to  stand,  carefully  covered,  for  several  hours ; 
then  add  more  nitric  acid,  evaporate  again  on  a  water-bath ;  next 
drive  off  the  sulphuric  acid  formed  and  finally  heat  over  a  Bunsen 
burner  (no  blast),  and  weigh  the  Sb2O4.  The  arsenic  will  be 
volatilized. 

Insoluble  Ores.  —  One  gram  of  the  6re  is  mixed  with  10  grams 
of  flux,  made  up  of  equal  parts  of  sodium  carbonate  and  sulphur, 
in  a  porcelain  crucible  and  covered  by  a  layer  of  the  same  flux. 
The  mixture  is  fused  for  about  ten  minutes,  covered,  in  the  muffle 
of  an  assay  furnace  or  by  a  Bunsen  burner.  The  heat  should  be 
low  at  first  and  gradually  raised,  but  never  high  enough  to  volatil- 
ize antimony.  The  melt  should  be  greenish;  if  it  is  yellow  the 
decomposition  is  probably  incomplete  unless  there  is  scarcely  any 
iron  present.  The  melt  is  treated  with  hot  water  and  the  sulphides 
of  iron,  lead,  etc.  (those  which  do  not  form  soluble  sulphosalts),  fil- 
tered out.  In  the  filtrate  the  antimony  is  precipitated  as  sulphide 
by  hydrochloric  acid  and  the  precipitate  treated  as  just  described. 

This  is  Rose's  method  of  decomposition  and  it  is  also  efficacious 
for  the  breaking  up  of  cassiterite.  Partially  soluble  ores  can  be 
treated  as  insoluble  or  treated  first  like  soluble  ores  and  the 
residue  fused. 

Properties  of  Antimony  Sulphide.  —  Insoluble  in  water  and  dilute 
acids ;  decomposed  by  concentrated  nitric  or  sulphuric ;  soluble 
in  concentrated  hydrochloric ;  easily  soluble  in  potassium  or  so- 
dium hydroxide  and  alkali  sulphides.  Slightly  soluble  in  ammonia 
and  ammonium  carbonate.  The  separation  from  arsenic  by  dis- 
solving the  sulphide  of  arsenic  in  ammonium  carbonate  is  not 
quantitative.  A  better  separation  is  Pattinson's.  Obtain  the  arsenic 


io6  QUANTITATIVE   ANALYSIS. 

and  antimony  in  solution  in  the  triad  condition,  add  concentrated 
hydrochloric  acid,  so  that  the  sp.  gr.  due  to  the  acid  shall  exceed 
1.17,  and  then  precipitate  the  arsenic  as  sulphide.  Arsenic  sul- 
phide is  insoluble  in  concentrated  hydrochloric  acid,  while  in  acid 
of  1.17  sp.  gr.  or  over  no  antimony  is  precipitated. 

Other  methods  of  separating  arsenic  and  antimony  will  be  given 
under  arsenic. 

VOLUMETRIC    METHODS. 

WELLER'S  METHOD.* 

The  ore  is  decomposed  as  already  described  and  the  antimony 
precipitated  as  sulphide,  if  arsenic  is  also  present  it  must  be  sepa- 
rated. As  tin  does  not  interfere  in  this  method  Pattinson's  sepa- 
ration can  be  used  with  stannous  chloride  to  reduce  the  arsenic 
to  arsenious  chloride  so  that  it  will  be  promptly  and  completely 
separated  as  arsenious  sulphide  in  the  strong  hydrochloric  acid 
solution;  then,  after  diluting  the  filtrate,  the  antimony  is  precipi- 
tated as  sulphide,  Sb2S3.  Or  the  arsenic  can  be  distilled  off  as 
arsenious  chloride  according  to  Fischer's  distillation  method  (see 
next  chapter). 

The  precipitated  sulphide  of  antimony  is  dissolved  in  strong  hy- 
drochloric acid  and  is  oxidized  to  the  pentad  condition  by  adding 
potassium  or  sodium  chlorate  in  small  portions  and  boiling  till  the 
excess  of  chlorine  is  expelled  and  the  oxides  of  chlorine  driven 
out.  It  is  essential  that  the  oxidation  shall  be  complete  and  all 
excess  of  oxidizing  agent  expelled,  as  the  method  depends  on 
measuring  the  iodine  liberated  by  the  pentad  antimony;  using  a 
standard  thiosulphate  solution,  as  with  copper. 

After  oxidation  the  solution  is  boiled  down  to  very  nearly  50 
c.c. ;  this  is  ascertained  with  sufficient  accuracy  by  making  a  mark 
on  the  beaker ;  then  20  c.c.  of  concentrated  hydrochloric  acid  are 
added  and  the  solution  diluted  to  600-700  c.c.  with  recently  boiled 
cold  water.  Then  three  grams  of  potassium  iodide  are  added  and 
after  waiting  a  few  minutes  for  the  solution  of  the  potassium  iodide 
and  the  liberation  of  the  iodine,  the  solution  is  titrated  by  sodium 
thiosulphate,  using  starch  solution  as  indicator,  till  the  blue  color 
disappears.  The  end  point  is  very  sharp  and  satisfactory  when 
these  conditions  are  maintained  exactly.  It  is  very  important  that 
the  amount  of  hydrochloric  acid  is  kept  constant;  if  too  little  is 

*Youtz,  SCHOOL  OF  MINES  QUARTERLY,  July,  1903. 


THE   DETERMINATION    OF   ANTIMONY.        107 

present  basic  iodides  and  chlorides  of  antimony  separate  out  on 
dilution  ;  if  too  much,  the  hydrochloric  acid  itself  acts  on  the 
potassium  iodide  in  the  presence  of  air  and  liberates  iodine.  We 
obtain  this  constant  quantity,  no  matter  how  much  may  be  used 
in  the  solution  of  the  sulphide,  by  boiling  down  to  50  c.c. ;  this 
will  be  acid  of  20  per  cent.,  the  hydrochloric  acid  of  constant  boil- 
ing point.  If  it  was  weaker  in  the  beginning,  more  water  boils  off, 
if  stronger,  more  hydrochloric  acid,  until  this  strength  of  acid  is 
reached.  So  by  this  means  we  obtain  always  the  equivalent  of  45 
c.c.  of  concentrated  hydrochloric  acid  in  a  volume  of  about  650  c.c. 

The  potassium  iodide  must  be  three  grams,  if  more  is  used 
results  which  are  too  high  are  obtained.  The  liberation  of  iodine 
is  not  instantaneous  so  it  is  advisable  to  wait  several  minutes 
before  titrating,  otherwise  the  solution  may  be  decolorized  by  the 
thiosulphate  and  then  the  blue  color  suddenly  flashes  back,  because 
the  reaction  is  not  yet  complete.  When  the  end  point  is  reached, 
under  the  right  conditions,  the  decolorization  lasts  for  several 
minutes. 

The  sodium  thiosulphate  solution  used  for  the  copper  assay  can 
be  used  here.  Theoretically  the  standard  against  antimony  would 
be  obtained  as  follows:  Copper  standard:  antimony  standard:: 
atomic  weight  copper:  one  half  atomic  weight  antimony.  It  has, 
however,  been  found  that  while  the  standards  obtained  from  copper, 
from  potassium  dichromate  and  from  iodine  agree  with  each 
other,  that  they  do  not  agree,  when  calculated  to  antimony,  with 
the  results  obtained  by  standardizing  with  pure  antimony.  The 
discrepancy  is  almost  exactly  one  per  cent.,  under  the  conditions 
for  titration  just  given ;  so  if  the  antimony  standard  is  to  be  calcu- 
lated from  any  of  the  others,  one  per  cent,  should  be  added  to  that 
standard.  If  the  calculated  standard  is  0.0062  grams  Sb  the  figure 
0.006262  should  be  used  under  the  conditions  given,  or  if  the  ore 
contained  by  calculation  18  per  cent,  the  percentage  of  anti- 
mony is  1 8. 1 8.  The  true  cause  of  this  variation  has  not  yet  been 
explained  but  the  same  deviation  has  also  been  observed  with 
arsenic.  It  is  more  satisfactory  to  restandardize  against  antimony 
if  absolutely  pure  metallic  antimony  can  be  obtained.  Weigh  out 
about  0.2  gram  and  dissolve  this  in  about  50  c.c.  or  more  of  con- 
centrated hydrochloric  acid  with  1-2  c.c.  of  concentrated  nitric 
acid,  then  complete  the  oxidation  by  adding  portions  of  0.5  gram 
of  potassium  or  sodium  chlorate,  boil  out  the  oxides  of  chlorine 


io8  QUANTITATIVE    ANALYSIS. 

and  proceed  as  described.     No  tartaric  acid  is  used  in  this  method. 
The  reaction  may  be  indicated  as  follows : 

Sb205  +  4HI  =  Sb203  +  2l2  +  2H20. 

The  antimony  after  oxidation  is  probably  present  as  antimonic 
acid  and  after  reduction  by  hydriodic  acid  it  is  present  partly  as 
antimonious  iodide  and  partly  as  antimonious  chloride,  depending 
on  the  relative  mass  of  hydriodic  and  hydrochloric  acids.  As  tin 
in  the  stannic  condition  is  not  reduced  by  hydriodic  acid,  anti- 
mony can  be  determined  in  the  presence  of  tin.  This  is  of  im- 
portance in  the  analysis  of  alloys. 

This  method  is  not  free  from  theoretical  difficulties,  but  it  is  very 
rapid  and  gives  excellent  practical  results  when  the  proper  condi- 
tions are  maintained.  The  same  thiosulphate  solution  can  be  used 
as  for  copper  and  the  end  point  is  sharp. 

MOHR'S  METHOD. 

This  is  exactly  the  reverse  of  Weller's  method.  The  reactions 
can  be  indicated  as  follows : 

Mohr  s->-  -<-«  Weller 

Sb203  +  2l2  +  2H20  ^t  Sb205  +  4HI. 

In  Mohr's  method  we  prevent  the  reverse  reaction  by  preventing 
any  concentration  of  hydriodic  acid  by  having  an  excess  of  alkali 
present.  In  order  not  to  decompose  the  starch  or  absorb  iodine 
this  excess  of  alkali  must  be  bicarbonate,  so  the  exact  reaction 
becomes 

Na3Sb03  +  I2  +  2NaHC03  =  Na3SbO4  +  2NaI  +  H2O  +  2CO2. 

The  same  statement  and  a  similar  reaction  applies  also  to  arsenic 
so  it  is  evident  that  no  arsenic  can  be  present. 

When  the  antimony  is  in  the  pentad  condition  it  must  be  re- 
duced by  heating  with  sulphurous  acid.  To  the  acid  solution  add 
30  c.c.  of  sulphurous  acid  (about  5  per  cent.  SO2)  and  boil  till  most 
of  the  sulphur  dioxide  is  expelled,  then  add  a  second  portion  of 
30  c.c.  and  boil  out  the  sulphur  dioxide  completely,  then  add 
about  two  grams  of  tartaric  acid,  to  prevent  the  subsequent  pre- 
cipitation of  antimony  as  hydrated  oxide  and  make  the  solution 
alkaline  with  sodium  bicarbonate,  add  about  20  c.c.  of  a  saturated 


THE    DETERMINATION    OF   ANTIMONY.         109 

solution  in  excess,  cool  and  titrate  with  N/io  iodine,  using  starch 
as  indicator,  at  a  volume  of  about  200  c.c. 

When  the  antimony  is  separated  as  sulphide,  either  Sb2S3  or 
Sb2  S5,  it  is  dissolved  in  hydrochloric  acid.  This,  by  the  liberation 
of  hydrogen  sulphide,  reduces  the  antimony  to  antimonious 
chloride,  so  that  after  adding  tartaric  acid  and  neutralizing  the 
excess  of  acid  by  alkali,  and  then  adding  an  excess  of  sodium 
bicarbonate  it  is  ready  for  titration. 

It  is  advisable  to  run  a  blank  made  by  neutralizing  the  same 
amount  of  hydrochloric  acid  in  the  same  way  and  adding  the  same 
excess  of  sodium  bicarbonate,  in  order  to  see  whether  a  small 
quantity  of  iodine  is  required  when  there  is  no  antimony  present. 
If  this  amounts  to  more  than  o.i  c.c.  it  should  be  subtracted. 

This  method  can  be  used  for  arsenic  in  exactly  the  same  way, 
omitting  the  tartaric  acid. 

Conclusion.  —  Formerly  antimony  was  weighed  as  sulphide, 
after  washing  with  alcohol,  to  remove  the  water,  then  with  carbon 
bisulphide  to  take  out  the  free  sulphur  and  drying  at  250°  C.  The 
results  are  always  high  and  the  method  is  only  to  be  used  for  very 
small  quantities,  under  I  per  cent.  A  comparison  of  results  has 
shown  the  weighing  as  oxide  to  be  slightly  low  and  that  the  Mohr 
and  Weller  methods  give  accurate  results. 

The  application  of  the  volumetric  methods  to  insoluble  ores  con- 
taining both  arsenic  and  antimony  will  be  indicated  in  the  next 
chapter. 


no  QUANTITATIVE   ANALYSIS. 

CHAPTER    XIV. 
The  Determination  of  Arsenic  in  Ores. 

DISTILLATION  METHOD. 

This  method  consists  in  distilling  off  the  arsenic  as  arsenious 
chloride,  and  so  affords  a  most  perfect  separation  from  antimony 
and  tin.  Although  it  requires  considerable  apparatus,  it  must  be 
regarded  as  the  standard  method  of  separation  ;  besides  being  ap- 
plicable to  ores  it  is  even  better  for  material  containing  only  very 
low  percentages  of  arsenic, — pig  copper,  etc.  It  was  devised  by 
Professor  Emil  Fischer,  of  Berlin. 

Arsenic  ores  are  almost  always  sulphides,  they  may  be  decom- 
posed by  the  fusion  methods  given  under  antimony,  and  the 
arsenic  precipitated  as  sulphide.  The  original  ore,  or  the  sixth- 
group  sulphides,  are  treated  as  follows  :  Place  about  two  grams  of 
potassium  chlorate  on  the  bottom  of  a  beaker ;  on  this  place  the 
weighed  sample  of  ore,  from  o.  5  to  3  grams,  depending  on  the  rich- 
ness, or  the  precipitated  sulphides  ;  then  about  a  gram  more  of 
potassium  or  sodium  chlorate,  sufficient  to  cover  the  ore ;  pour  in 
cautiously  little  by  little  a  mixture  of  30  c.c.  of  concentrated  hy- 
drochloric acid  and  10  c.c.  of  water,  cover  the  beaker  and  heat  on 
a  water-bath  till  the  decomposition  is  complete  and  the  oxides  of 
chlorine,  etc.,  driven  off  so  as  not  to  use  up  the  ferrous  salt  added 
later.  It  is  very  important  that  the  oxidation  is  complete  to 
H3AsO4,  as  the  arsenious  chloride  would  be  lost  by  boiling.  If 
antimony  is  also  to  be  determined,  filter  off  any  residue  on  asbestos, 
transfer  the  solution  to  a  distilling  flask  (about  400  c.c.)  using  concen- 
trated hydrochloric  acid  to  rinse  out  the  beaker,  etc.,  add  5  to  20 
grams  of  ferrous  sulphate,  depending  on  the  quantity  of  arsenic  pres- 
ent and  make  the  solution  up  to  about  200  c.c.  in  volume  with  con- 
centrated hydrochloric  acid.  Connect  the  flask  with  a  short  con- 
denser and  under  the  end  place  an  Erlenmeyer  flask,  about  250  c.c., 
containing  a  little  water  so  as  to  cover  the  end  of  the  condenser 
tube.  Heat  the  flask  on  an  asbestos  pad  by  a  burner ;  the  arsenic 
acid  is  promptly  reduced  by  the  large  excess  of  ferrous  salt  and 
forms  arsenious  chloride  ;  this  with  hydrochloric  acid  begins  to 
distill  over  before  a  temperature  of  100°  C.  is  reached.  They  are 


THE    DETERMINATION    OF   ARSENIC.  in 

condensed  and  collect  in  the  Erlenmeyer  flask.  If  this  becomes 
very  hot  it  should  be  surrounded  by  ice  water.  The  apparatus 
should  be  set  up  in  a  place  free  from  draughts  so  as  to  avoid  back 
pressure.  The  distillation  is  continued  until  about  half  the  original 
volume  remains.  Remove  the  Erlenmeyer  flask  and  then  the 
burner,  when  cool  aold  another  100  c.c.  of  concentrated  hydro- 
chloric acid  and  repeat  the  distillation,  catching  the  distillate  as 
before.  This  is  continued  till  no  more  arsenic  distills  over,  which 
can  easily  be  ascertained  by  testing  a  portion  of  the  last  distillate 
with  hydrogen  sulphide.  Unless  there  is  a  very  large  quantity  of 
arsenic  present  two  or  at  most  three  distillations  are  all  that  are 
required.  The  solution  in  the  flask  must  not  be  allowed  to  be- 
come too  small  or  in  other  words  the  boiling  point  must  not  be 
allowed  to  rise  above  107°  C.  for  the  temperature  of  the  vapor 
and  112°  C.  for  the  solution  ;  above  this  point  antimony  will  be- 
gin to  distill  over.  The  distillation  can  be  hastened  by  connect- 
ing the  distilling  flask  with  a  second  flask  containing  concentrated 
hydrochloric  acid,  this  is  heated  so  that  a  stream  of  hydrochloric 
acid  gas  passes  in  constantly,  so  that  the  strength  of  the  acid  is 
maintained  and  the  removal  of  the  arsenious  chloride  facilitated 
(like  distilling  with  steam). 

When  the  separation  is  complete,  the  apparatus  is  allowed  to 
cool  and  the  antimony  from  the  distilling  flask  is  precipitated  by 
hydrogen  sulphide  after  diluting  largely  and  the  antimony  sul- 
phide treated  as  already  described.  The  arsenic  is  all  in  the  dis- 
tillate in  the  arsenious  condition  ;  it  can  be  determined  by  nearly 
neutralizing  the  large  excess  of  acid  by  soda,  then  adding  a  strong 
solution  of  sodium  bicarbonate  and  titrating  by  Njio  iodine,  ex- 
actly as  given  under  antimony. 

If  a  gravimetric  method  is  to  be  used  the  arsenic  is  precipitated 
by  hydrogen  sulphide  after  diluting  somewhat.  Under  these  con- 
ditions the  arsenic  precipitates  immediately  as  arsenious  sulphide 
with  very  little  sulphur,  as  it  is  entirely  in  the  triad  condition.  If 
the  amount  is  small  it  can  be  filtered  on  a  Gooch  crucible,  washed 
with  alcohol,  then  with  carbon  bisulphide  and  after  drying  at 
1 10°  C.  weighed  as  sulphide.  The  results  are  slightly  high.  If 
the  amount  of  arsenic  is  considerable,  over  20  per  cent.,  the  error 
will  increase  proportionally  and  the  arsenic  must  be  dissolved,  oxi- 
dized and  finally  weighed  as  magnesium  pyroarsenate.  The  siu- 
phide  is  dissolved  in  fuming  nitric  acid,  the  excess  of  acid  ana 


112  QUANTITATIVE   ANALYSIS. 

oxides  of  nitrogen  removed  by  boiling  (for  manipulation  compare 
antimony  sulphide  when  paper  is  used)  ;  or  dissolve  from  the 
Gooch  crucible  by  ammonia,  evaporate  down  on  a  water-bath  and 
then  oxidize,  or  dissolve  through  by  a  small  quantity  of  sodium 
hydroxide  and  oxidize  by  boiling  with  bromine. 

PRECIPITATION  OF  MAGNESIUM  AMMONIUM  ARSENATE. 
The  conditions  for  the  precipitation  of  magnesium  ammonium 
arsenate  are  similar  to  those  for  magnesium  ammoniun  phosphate, 
but  as  the  precipitate  is  more  soluble  and  also  more  easily  decom- 
posed on  ignition  greater  care  must  be  used.  When  the  arsenic 
is  all  in  the  pentad  condition  neutralize  the  acid  solution  with 
ammonia  and  add  a  slight  excess.  The  volume  should  not 
exceed  100  c.c.;  add  magnesia  mixture  slowly,  drop  by  drop,  till 
in  considerable  excess,  then  alcohol  equal  to  one  third  the  volume 
of  the  solution  and  allow  to  stand  in  the  cold  over  night.  Filter  on 
asbestos  in  a  Gooch  crucible  and  wash  with  2^/2  per  cent,  ammonia 
containing  a  little  alcohol,  then  with  20  per  cent,  alcohol  alone,  dry 
and  ignite  very  gently  to  constant  weight ;  weigh  the  Mg2As2Or 

SEPARATIONS  OF  ARSENIC  AND  ANTIMONY. 

The  action  of  hydrogen  sulphide  on  arsenic  and  antimony  is 
important  but  confusing. 

The  following  separations  are  used  : 

Bunsen's  Method. — When  hydrogen  sulphide  is  passed  into  an 
acid  solution  containing  pentad  arsenic  and  pentad  antimony  at  the 
room  temperature  and  then  the  hydrogen  sulphide  driven  out  by 
a  current  of  air,  antimonic  sulphide,  Sb2S5,  only  is  precipitated. 
The  hydrogen  sulphide  reduces  the  arsenic  slowly,  and  if  the  ex- 
cess is  promptly  driven  out  when  the  precipitation  is  complete,  a 
satisfactory  separation  is  effected. 

Pattinsoris  Method.  —  In  the  separation  described  under  anti- 
mony the  hydrochloric  acid  was  so  strong  that  no  antimony  sul- 
phide could  form  ;  here  to  get  a  prompt  precipitation  of  arsenic  it 
should  be  reduced  before  passing  in  hydrogen  sulphide.  When 
stannous  chloride  is  used  care  must  be  taken  to  avoid  an  excess, 
which  would  precipitate  metallic  arsenic. 

Neher's  Method. — The  solution  containing  arsenic  and  antimony, 
completely  oxidized,  and  at  least  two  volumes  of  concentrated  hy- 
drochloric acid  to  one  of  solution  (i.  e.,  1. 14  sp.  gr.),  is  cooled  to  zero 


THE   DETERMINATION    OF   ARSENIC.          113 

and  saturated  by  a  rapid  stream  of  hydrogen  sulphide.  The  arsenic 
is  completely  precipitated  as  pentasulphide,  As2S5.  McCay  ob- 
tains the  same  result  by  saturating  the  solution  containing  pentad 
arsenic  in  the  cold  with  hydrogen  sulphide  and  then  heating  in  a 
closed  bottle  (under  pressure)  in  a  water-bath.  The  arsenic  can 
be  filtered  on  a  Gooch  crucible  and  weighed  as  pentasulphide, 
As2S5.  These  separations  are  in  accord  with  the  theory  that  in  a 
hot  solution  hydrogen  sulphide  reduces  the  arsenic  first  and  then 
precipitates  it  as  As2S3  mixed  with  sulphur ;  at  the  ordinary  tem- 
perature this  reduction  goes  on  slowly,  at  zero  it  is  not  perceptible. 
Also  as  the  acid  increases  the  amount  of  pentasulphide  increases. 
The  limit  being  Neher's  method  where  at  o°C.  and  in  a  strongly 
acid  solution  the  precipitation  is  entirely  as  As2S5.  So  under  or- 
dinary conditions  we  obtain  various  mixtures  of  As2S3,  As2S3  and 
S,  depending  on  the  temperature  and  the  acidity. 

For  information  on  the  formation  of  sulphoxy  acids  of  arsenic, 
which  by  breaking  up  give  these  sulphides,  see  McCay,  J.  Amer. 
Client.  Soc.t  24,  66 1,  1902.  And  for  more  information  on  the 
separation,  see  Treadwell's  "  Quantitative  Analysis,"  pp.  150-154 
(German  edition).  When  arsenic  is  to  be  removed  in  the  course 
of  analysis  with  the  fifth  and  sixth  groups,  it  should  be  reduced 
by  sulphurous  acid  and  the  excess  expelled.  This  is  accom- 
plished readily  under  pressure  by  heating  in  a  strong  bottle  in 
boiling  water,  wrapped  up  in  a  towel  to  prevent  flying  glass,  in 
case  of  an  explosion. 

VOLUMETRIC  METHODS. 

The  most  important  determination  of  arsenic  for  mining  engi- 
neers is  in  ores,  where  it  is  present  from  i-io  per  cent,  and  for 
this  determination  some  modification  of  Pearce's  method  is  usually 
employed.  The  method  is  not  free  from  objections  and  gives  low 
results  on  arsenopyrite.  This  method  and  one  recently  divised  by 
Danziger  and  Buckhout  *  which  is  also  applicable  to  arsenopyrite 
will  be  described. 

PEARCE'S  METHOD  AS  MODIFIED  BY  BENNET  f  is  based  on  the 
following  facts.  Arsenic  when  fused  with  a  mixture  of  potassium 
nitrate  and  sodium  carbonate  is  completely  oxidized  and  forms 

*  SCHOOL  OF  MINES  QUARTERLY,  April,  1903. 
•\  J.  Amer.  Chein.  Soc.,  21,  p.  431,  1899. 


H4  QUANTITATIVE   ANALYSIS. 

sodium  arsenate,  Na3AsO4,  which  is  soluble  in  water,  while  anti- 
mony forms  a  quite  insoluble  sodium  metantimoniate  which  is  left 
behind  when  the  melt  is  leached  with  water,  together  with  oxide 
of  iron,  insoluble  carbonates,  etc.  The  filtrate  contains  beside, 
Na3AsO4,  Na2SO4,  Na2SiO3,  Na2Al2O4  and  an  excess  of  Na2CO3 ; 
this  is  acidified  and  the  carbon  dioxide  expelled ;  then  neutralized 
exactly  and  the  arsenic  precipitated  as  silver  arsenate,  Ag3AsO4,  by 
an  aqueous  solution  of  silver  nitrate.  It  is  this  neutralization 
which  has  given  trouble  ;  in  the  original  method  it  was  effected  by 
ammonia,  but  as  the  precipitate  (Ag3AsO4)  is  readily  soluble  either 
in  nitric  acid  or  ammonia,  it  was  essential  to  obtain  exactly  the 
neutral  point.  The  second  plan  for  neutralizing  was  proposed  by 
Canby,  the  addition  of  a  cream  of  zinc  oxide  ;  this  method  will 
give  a  sufficiently  neutral  solution  if  the  zinc  oxide  is  allowed  to 
remain  in  contact  with  the  solution  over  night.  The  latest  sug- 
gestion is  that  of  Bennet  to  use  acetic  acid  and  a  sensitive  indicator 
like  phenolphthalein. 

The  precipitate  of  silver  arsenate  is  filtered  off  and  the  silver  in 
it  determined  by  Volhard's  thiocyanate  titration  using  ferric  alum 
as  an  indicator.  The  method  is  therefore  an  indirect  titration  of 
the  arsenic,  and  for  three  atoms  of  silver  found  there  must  have 
been  present  from  the  ore,  one  atom  of  arsenic.  So  the  arsenic 
value  for  the  thiocyanate  solution  is  obtained  from  the  silver  stand- 
ard by  using  the  proportion, —  atomic  weight  silver  to  one  third 
atomic  weight  arsenic. 

Solutions  Required.  —  Aqueous  nitrate  of  silver,  made  by  dissolv- 
ing silver  nitrate  crystals  in  water.  (The  nitric  acid  solution  used 
to  test  for  chlorides  will  not  do  here.) 

A  ten  per  cent,  solution  of  ferric  sulphate  or  a  saturated  solution 
of  iron  ammonium  alum  as  indicator ;  a  solution  of  ammonium 
thiocyanate  containing  about  8  grams  per  liter.  This  is  standard- 
ized by  dissolving  portions  of  pure  silver,  about  0.2  gram  each  in 
nitric  acid,  1.16  sp.  gr.  diluting  to  about  100  c.c.  ;  adding  5  c.c. 
of  the  indicator  and  titrating  until  a  faint  permanent  reddish  color 
is  produced.  The  silver  is  precipitated  as  thiocyanate.  The  end 
point  is  the  production  of  red  ferric  thiocyanate. 

Both  standards  should  be  placed  on  the  bottle  as  the  solution 
may  be  used  for  the  determination  of  silver  in  alloys,  etc.  This 
solution  keeps  well  and  therefore  does  not  require  frequent  re- 
standardizing. 


THE   DETERMINATION    OF   ARSENIC.  115 

Flux. —  Make  up  a  sufficient  quantity  of  flux  containing  two  parts 
of  potassium  nitrate  by  weight,  to  one  part  of  sodium  carbonate. 

Assay.  —  Place  a  layer  of  the  flux  on  the  bottom  of  a  Russia 
iron  crucible,  mix  the  weighed  portion  of  the  ore,  0.25  to  I 
gram,  depending  on  the  quantity  of  arsenic,  with  8-10  times  its 
weight  of  the  flux  and  place  this  on  top  of  the  first  layer ;  cover 
this  with  a  layer  of  potassium  nitrate.  Porcelain  crucibles  may 
be  used,  but  they  usually  break,  owing  to  the  contraction  of  the 
flux  on  cooling. 

Heat  the  crucible  very  gently  and  gradually,  holding  the 
burner  in  the  hand  and  allowing  the  flame  to  heat  different  parts 
of  the  crudible  in  turn.  The  heating  requires  attention  or  arsenic 
will  be  lost  with  a  high-grade  ore.  There  must  be  no  odor  or 
fumes  of  arsenic  at  this  point.  After  the  fusion  has  become  quiet, 
the  heating  is  continued  for  several  minutes  and  the  contents 
caused  to  rotate  to  ensure  complete  fusion  and  oxidation.  Allow 
to  cool  and  leach  with  hot  water,  filter  and  wash  the  residue  very 
thoroughly  with  hot  water  ;  acidify  with  nitric  acid  and  boil 
vigorously  till  all  the  carbon  dioxide  is  expelled.  If  any  precepitate, 
such  as  hydrated  silica,  forms  here  it  may  be  filtered  out,  as  it 
would  interfere  with  the  filtration  of  the  silver  arsenate,  but  not 
with  the  accuracy  of  the  results.  Allow  the  solution  to  cool 
completely ;  add  a  few  drops  of  phenolphthaleine  and  then 
dilute  sodium  hydroxide  solution  (not  ammonia  or  sodium  car- 
bonate on  account  of  the  indicator)  till  the  solution  turns  pink, 
then  acetic  acid  drop  by  drop  till  the  color  is  discharged,  stirring 
between  each  addition,  so  as  to  stop  when  there  is  but  a  drop  of 
acetic  acid  in  excess.  Then,  to  the  cold  solution  add  a  slight  ex- 
cess of  aqueous  silver  nitrate,  filter  the  brick-red  silver  .arsenate 
and  wash  it  with  cold  water  till  free  from  silver.  As  silver  acetate 
is  sparingly  soluble,  this  must  be  completely  washed  out  as  well 
as  the  excess  of  nitrate.  Dissolve  the  precipitate  through  the  paper 
with  dilute  nitric  acid  into  a  clean  beaker;  dilute  to  about  100 
c.c.;  add  5  c.c.  of  the  ferric  indicator,  and  titrate  as  in  standard- 
izing. 

SODIUM  PEROXIDE  METHOD. 

Sodium  peroxide  has  been  found  to  be  an  admirable  reagent  for 
the  decomposition  of  arsenic  ores ;  its  action  is  the  same  as  the 
mixture  of  potassium  nitrate  and  sodium  carbonate  to  form  sodium 
arsenate,  but  it  acts  more  rapidly  and  effectively  in  preventing  loss 


ii6  QUANTITATIVE   ANALYSIS. 

by  volatilization  with  high-grade  ores.  After  destroying  the  ex- 
cess of  peroxide  and  filtering  off  the  residue,  we  have  an  alkaline 
solution  containing  sodium  arsenate.  There  are  at  least  three  volu- 
metric methods  by  which  the  arsenic  can  be  determined  :  (ist)  In- 
directly as  silver  arsenate  as  just  described,  (2nd)  by  standard  alkali. 
Acidify  the  alkaline  solution  with  hydrochloric  or  nitric  acid  in 
slight  excess,  boil  out  carbon  dioxide,  then  add  methyl  orange  and 
titrate  till  the  solution  turns  yellow,  with  a  dilute  solution  of  sod- 
ium hydroxide.  This  marks  the  neutralization  of  the  excess  of 
hydrochloric  or  nitric  acid  and  of  one  hydrogen  of  the  arsenic  acid  ; 
we  have  now  in  solution  NaH2  AsO4 ;  add  a  few  drops  of  phenol 
phthaleine,  and  titrate  to  a  pink  color  with  a  standard  solution  of 
sodium  hydroxide.  The  amount  of  alkali  used  is  that  required 
to  neutralize  the  second  hydrogen.  Hence  for  each  molecule  of 
sodium  hydroxide  used  there  is  present  one  atom  of  arsenic.  This 
method  is  only  outlined  as  it  is  not  as  accurate  as  the  others. 
Third  method  :  Measuring  the  arsenic  present  by  the  amount 
of  iodine  liberated,  as  in  Weller's  method  for  antimony.  This 
gives  accurate  results  when  carried  out  as  follows  :  About  half  a 
gram  of  arsenopyrite  or  more  of  an  ore  containing  less  arsenic 
is  mixed  with  10-15  grams  of  sodium  peroxide  and  placed  in  a  large 
nickel  crucible,  so  that  it  is  not  more  than  one  third  full,  with 
a  cover  of  sodium  peroxide  on  top.  The  crucible  is  heated  slowly 
at  first,  until  the  mass  is  fused,  then  the  temperature  is  raised  to  a 
strong  red  heat  for  a  couple  of  minutes,  the  crucible  is  held  by 
tongs  in  the  flame  and  the  contents  caused  to  rotate.*  Allow  to 
cool  and  leach  with  about  ipo  c.c.  of  hot  water,  then  boil  for  five 
minutes,  till  the  excess  of  sodium  peroxide  is  completely  decom- 
posed, filter  and  wash  with  hot  water  containing  sodium  carbonate. 
Acidify  with  hydrochloric  acid,  boil  out  the  carbon  dioxide  and 
evaporate  to  about  75  c.c.  When  cold,  add  about  75  c-c-  of  con- 
centrated hydrochloric  acid  and  allow  to  cool  again,  then  add  3 
grams  of  potassium  iodide  and  titrate  the  liberated  iodine  by  a 
standard  sodium  thiosulphate  solution,  till  only  a  faint  straw 
color,  due  to  free  iodine,  remains  ;  finish  the  titration,  using  starch 
solution  as  a  spot  test  on  a  white  tile,  till  no  blue  color  is  pro- 
duced. The  starch  does  not  give  satisfactory  results  when  added 
to  the  solution,  on  account  of  the  great  quantity  of  hydrochloric 
acid,  which  has  to  be  present  to  effect  the  quantitative  liberation 

*This  is  necessary  to  obtain  complete  decomposition  of  the  ore. 


THE   DETERMINATION    OF   ARSENIC.  n/ 

of  iodine.  Pink  and  violet  colors  are  formed  which  give  an 
uncertain  end  point.  The  spot  test  is  not  tiresome  in  this  case 
because  it  is  possible  to  judge  the  end  within  a  few  drops  by  the 
yellow  color  of  the  solution. 

As  in  the  case  of  the  antimony  titration,  the  results,  using  the 
standard  calculated  from  iodine  or  potassium  dichromate,  are  about 
I  per  cent.  low.  So  that  I  per  cent,  of  the  arsenic  present  should 
be  added  to  the  results  ;  or  better,  standardize  against  freshly  re- 
sublimed  arsenious  oxide,  As4O6,  as  follows  :  Weigh  out  portions 
of  0.2-0.25  gram  of  resublimed  arsenious  oxide  into  small  beakers  ; 
add  to  each  about  0.5  gram  of  potassium  chlorate  and  about  20  c.c. 
of  concentrated  hydrochloric  acid  and  boil  till  the  oxidation  of  the 
arsenic  is  complete  and  all  yellow  color  has  disappeared  from  the 
solution  ;  add  water  and  concentrated  hydrochloric  acid  so  that 
the  final  bulk  is  100-150  c.c.  and  consists  of  half  concentrated 
hydrochloric  acid  and  half  water  (20  per  cent,  actual  HC1).  Cool, 
add  three  grams  of  potassium  iodide  and  titrate  as  in  the  ore. 
Calculate  the  arsenic  standard  'from  the  number  of  c.c.  used. 
This  is  another  titration  where  the  results  are  varied  by  changes 
in  the  conditions  of  titration  ;  here  the  important  points  are  the  tem- 
perature, the  acidity  and  the  amount  of  potassium  iodide.  When 
uniform  conditions  are  maintained  in  standardizing  and  in  titrating 
the  results  are  very  exact. 

It  only  remains  to  indicate  a  procedure  for  ores  containing  both 
arsenic  and  antimony.  Decompose  the  ore  with  sodium  peroxide, 
as  given,  leach,  boil,  filter  and  precipitate  the  antimony  by  Bunsen's 
method  (page  112),  filter  out  the  antimonic  sulphide  and  titrate 
the  arsenic  in  the  filtrate  as  just  described.  To  obtain  the  anti- 
mony dissolve  the  residue  from  the  fusion  in  hydrochloric  acid, 
filter,  precipitate  the  antimony  in  the  filtrate  by  hydrogen  sulphide  ; 
add  this  to  the  sulphide  already  obtained  :  dissolve  and  titrate  by 
either  of  the  methods  given  under  antimony  ore. 

ADDITIONAL  REFERENCES  TO  BOTH  ARSENIC  AND  ANTIMONY. 

Review  of  methods  for  antimony,  Z.fur  Analytische  Chemie,  38, 
p.  664,  1899;  for  arsenic;  same,  39,  pp.  654-670  and  699-720, 
1900.  Beck  and  Fisher,  Separation  and  Estimation  of  Arsenic 
and  Antimony  in  Ores,  SCHOOL  OF  MINES  QUARTERLY,  20,  372. 


ii8  QUANTITATIVE   ANALYSIS. 


CHAPTER  XV. 

Slag  Analysis. 

Under  the  title  of  Slag  Analysis,  nearly  the  whole  subject  of 
analytical  chemistry  and  assaying  might  be  discussed,  for  a  great 
majority  of  the  elements,  both  common  and  rare,  are  to  be  found 
in  slags.  No  such  attempt  will  be  made  here  ;  what  follows  is 
merely  a  description  of  the  technical  analysis  of  some  of  the  most 
important  types  of  slags. .  For  a  more  detailed  and  complete  dis- 
cussion of  the  subject  the  reader  is  referred  to  an  article  by  Dr. 
Jouet  on  the  Analysis  of  Slags  and  Cinders,  in  the  SCHOOL  OF 
MINES  QUARTERLY,  Vol.  XXII.,  Nos.  i  and  2. 

If  the  sample  of  slag  has  been  chilled  suddenly,  it  can  usually 
be  decomposed  by  acids,  if  allowed  to  cool  slowly,  a  fusion  with 
mixed  carbonates  is  required.  The  important  points  to  be  shown 
in  a  technical  analysis  are  :  The  ratio  of  bases  to  silica,  the  ratio  of 
R2O8  bases  to  those  of  the  RO  type,  the  quantity  of  valuable 
metal  present  in  a  slag,  from  copper  smelting,  copper,  etc. 

For  convenience  in  treating  this  subject  the  following  classifica- 
tion is  made  ; 

Iron  Slags.  —  The  slags  from  the  blast  furnace  in  the  produc- 
tion of  pig  iron,  though  containing  much  less  iron  than  those 
which  follow.  They  contain  roughly  40-50  per  cent,  silica,  I  5- 
20  per  cent,  alumina,  etc.,  30—40  per  cent,  lime,  magnesia,  etc., 
besides  iron,  manganese,  alkalies,  sulphur,  phosphorus,  etc.  The 
slags  from  basic  processes  are  often  rich  in  phosphoric  acid.  For 
this  determination  see  Bulletin  46,  Division  of  Chemistry,  U.  S. 
Department  of  Agriculture  or  Wiley's  Agricultural  Analysis, 
Vol.  II. 

Manganese  Slags.  —  The  slags  formed  in  the  production  of 
Spiegel,  lower  in  silica  than  the  iron  slags,  but  containing  up  to  ten 
per  cent,  of  manganese.  The  difficult  points  in  their  analysis  are 
the  decomposition  and  the  separation  of  manganese  from  alumina. 

Lead  Slags.  —  Containing  roughly  silica  32  percent.,  iron  28 
per  cent.,  lime,  etc.,  20  per  cent.,  the  remainder  being  lead,  zinc, 
antimony,  sulphur,  etc. 


SLAG   ANALYSIS.  119 

Copper  Slags.  —  Similar  in  composition  to  the  lead  slags,  but 
usually  without  lead  or  zinc  and  containing  about  half  a  per  cent, 
of  copper. 

These  four  groups  of  slags  fall  naturally  into  two  divisions,  the 
iron  and  manganese  slags  and  the  lead  and  copper  slags. 

A  general  scheme  will  be  given  for  each  of  these  divisions,  fol- 
lowed by  a  few  comments  and  special  precautions  and  by  some 
separate  methods  for  the  determination  of  particular  constituents. 
The  methods  will  not  be  given  in  detail  as  they  have  already  been 
discussed  in  these  notes. 

IRON  AND  MANGANESE  SLAGS. 

In  this  scheme  (page  1 20)  provision  has  been  made  for  titanium, 
barium,  zinc,  nickel  and  cobalt  and  also  for  the  removal  of  the 
higher  groups,  although  they  are  not  usually  present.  When 
these  are  omitted  the  analysis  becomes  quite  similar  to  that  of  lime- 
stone. Phosphorus  and  sulphur  must  be  determined  in  separate 
portions.  See  Iron  Ore. 

In  manganese  slags,  the  fusion  with  mixed  carbonates  will  usu- 
ally be  required  to  get  complete  decomposition,  using  a  liberal 
quantity  of  flux  and  a  long  fusion.  In  making  the  basic  acetate 
separation,  the  excess  of  acetic  acid  must  be  very  small  in  order 
to  get  complete  precipitation  of  alumina  and  must  be  repeated  to 
remove  the  manganese  which  is  sure  to  come  down  under  these 
conditions. 

The  determinations  of  greatest  importance  and  in  many  cases 
all  that  is  required,  are  silica,  oxides  of  iron  and  alumina,  lime  and 
magnesia.  When  the  slag  is  soluble  and  only  approximate  results 
are  required  the  determinations  can  be  made  as  follows  :  * 

Portion  for  silica  and  oxides  of  iron  and  alumina.  Weigh  out  half 
a  gram  of  the  sample,  place  this  in  a  casserole,  add  about  20  c.c. 
of  water  and  stir  well,  then  15-20  c.c.  of  strong  hydrochloric  acid, 
heat  to  boiling,  while  stirring  to  break  up  any  lumps  ;  then  evap- 
orate rapidly  to  dryness  and  bake,  take  up  with  hydrochloric 
acid  and  water,  boil  and  filter,  ignite  and  weigh  the  silica  (impure). 
In  the  filtrate  the  alumina  is  precipitated,  together  with  ferric  hy- 
droxide, by  ammonia  and  ammonium  chloride.  This  should  be 
reprecipitated,  to  free  it  from  lime  and  magnesia,  then  ignited  and 
weighed  as  usual. 

*  See  also  Lord's  "Notes  on  Metallurgical  Analysis,"  p.  201  and  seq. 


1 20 


QUANTITATIVE   ANALYSIS. 


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SLAG    ANALYSIS.  121 

Portion  for  lime  and  alumina.  Treat  a  gram  as  above,  using 
more  water  and  acid  ;  evaporate  to  dryness  and  heat  to  dehy- 
drate the  gelatinous  silica ;  add  hydrochloric  acid  and  water, 
boil,  pour  into  a  5OO-c.c.  flask,  rinse  out  the  casserole  with  more 
hydrochloric  acid  and  water,  adding  this  also  to  the  flask  ;  dilute 
to  about  300  c.c.,  add  ammonia  in  slight  excess,  dilute  to  the 
mark  (500  c.c.),  mix  thoroughly;  filter  through  a  dry  paper  and 
determine  lime  and  magnesia  in  an  aliquot  part  (250  or  200  c.c.) 
by  the  usual  methods. 

Lime  may  be  precipitated  as  oxalate  in  the  filtrate  from  silica 
without  removing  iron  and  alumina ;  the  filtrate  is  heated  to  boil- 
ing and  a  slight  excess  of  ammonia  is  added,  then  an  oxalic  acid 
solution,  more  than  enough  to  combine  with  the  lime,  then  am- 
monia is  added  again  and  finally  enough  oxalic  acid  to  redissolve 
any  iron.  The  solution  is  heated  to  boiling  and  the  calcium  oxa- 
late filtered  and  either  weighed  or  titrated  as  usual.  The  object 
here  is  to  get  sufficient  oxalic  acid  to  prevent  the  precipitation  of 
iron.  The  method  is  not  accurate  and  is  spoiled  by  the  presence 
of  manganese. 

None  of  these  short  methods  is  applicable  to  manganese  slags. 

LEAD  AND  COPPER  SLAGS/ 

If  silver  is  present  it  will  be  largely  with  the  first  residue  of 
silica,  lead  sulphate,  etc.  In  this  case  it  should  be  leached  with 
ammonia  before  removing  the  lead  sulphate. 

In  the  scheme  given  (page  122)  the  barium  is  likely  to  be  low,  as 
the  barium  sulphate  is  somewhat  soluble  in  ammonium  acetate  and 
also  on  account  of  the  final  reprecipitation  in  the  presence  of  hy- 
drochloric and  tartaric  acids.  When  barium  is  absent  and  the 
antimony  in  the  residue  disregarded  this  portion  of  the  analysis 
becomes  very  simple. 

Similarly  in  the  main  filtrate,  if  the  trace  of  lead  which  escapes 
precipitation  as  sulphate  is  disregarded  and  bismuth  is  absent 
the  fifth-group  sulphides  may  be  dissolved  and  the  copper  titrated 
at  once. 

It  is  not  advisable  to  employ  the  volumetric  method  for  anti- 
mony here  as  the  amount  is  small  and  difficult  to  dissolve  from 
the  sulphur  thrown  down  with  it. 

In  treating  the  filtrate  for  iron,  ammonia  may  be  used  instead 
of  the  basic  acetate  if  manganese  is  absent.  The  percentage  of 


122 


QUANTITATIVE    ANALYSIS. 


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SLAG   ANALYSIS.  123 

iron  is  usually  high  and  no  particular  difficulties  are  likely  to  be 
met. 

Sulphur  is  occasionally  determined  in  lead  slags.  This  is  either 
done  by  the  Fahlberg-Iles  method*  or  as  follows:f  One  gram 
of  the  slag  is  treated  in  a  casserole  with  a  few  c.c.  of  water,  10 
c.c.  of  concentrated  nitric  acid  and  finally  20-25  c.c.  of  concen- 
trated hydrochloric  acid  ;  boiled  for  about  ten  minutes,  more 
hydrochloric  acid  added,  and  then  evaporated  to  dryness  and 
baked  on  a  hot  plate.  When  cold  it  is  taken  up  with  concentrated 
hydrochloric  acid  and  water  and  boiled  thoroughly ;  then  the  free 
acid  neutralized  with  ammonia  and  exactly  six  c.c.  of  concentrated 
hydrochloric  acid  added  and  the  boiling  and  stirring  continued  till 
it  is  certain  that  all  the  iron  oxide  and  lead  sulphate  are  in  solu- 
tion;  diluted  to  200  c.c.,  25  c.c.  of  10  per  cent,  barium  chloride 
added  and  the  solution  boiled  for  i  5  to  20  minutes,  filtered  and 
washed.  The  precipitate  is  ignited  in  a  platimum  crucible,  the 
silica  driven  off  by  hydrochloric  and  sulphuric  acids  and  the 
barium  sulphate  weighed.  If  the  slag  is  not  chilled,  it  will  not  be 
decomposed  thoroughly,  so  the  barium  sulphate  will  be  impure. 
With  soluble  slags  this  method  gives  good  results  and  is  much 
shorter  than  the  Fahlberg-Iles. 

When  the  results  are  required  in  a  very  short  time  accuracy 
must  give  way  to  rapidity.  So  time  is  saved  by  working  at  once 
on  a  number  of  separate  portions.  (See  Furman's  "  Manual  on 
Assaying.") 

The  following  methods  are  employed  for  these  slags  : 

Silica.  —  Dissolve  half  a  gram  in  water  and  hydrochloric  acid, 
filter,  ignite  and  weigh  the  silica  (which  is  of  course  impure). 

Barium.  —  Dissolve  half  a  gram  in  hydrochloric  acid,  add  sul- 
phuric acid  and  evaporate  to  fumes,  neutralize  the  excess  of  sul- 
phuric acid  by  ammonia,  add  6  c.c.  of  hydrochloric  acid,  dilute 
to  200  c.c.,  boil  and  filter,  weigh  the  silica  and  barium  sulphate. 

Iron.  —  i  gram  is  dissolved  and  the  iron  titrated  by  either  the 
dichromate  or  the  permanganate  method. 

Manganese.  —  i  gram,  using  Volhard's  method. 

Zinc.  —  i  gram  by  the  ferrocyanide  method. 

*Iles,  Decomposition  and  Analysis  of  Slags,  SCHOOL  OF  MINES  QUARTERLY,  V.,  p. 

357- 

f  Miller  and  Thompson,  paper  read  at  N.  Y.  Section  American  Chem.  Soc. ,  Decem- 
ber 4,  1903. 


124  QUANTITATIVE   ANALYSIS. 

Copper.  —  I  gram  or  more  by  the  colorimetric  method. 

Lead.  —  i  gram  or  more  by  volumetric  methods  or  a  larger 
portion  by  fire  assay. 

Silver  is  usually  determined  by  fire  assay. 

The  other  determinations  have  been  indicated  under  the  iron 
and  manganese  slags. 

When  ferrous  iron  is  to  be  determined,  Cooke's  method,  as 
given  by  Hillebrand,  Bulletin  176,  U.  S.  Geological  Survey,  p.  92, 
is  to  be  used. 

Objection  can  easily  be  made  to  these  schemes  ;  they  are  in- 
complete on  one  hand  and  too  long  for  some  purposes  on  the 
other  ;  but  they  are  given  as  representing  as  much  as  is  likely  to 
be  required  of  the  mining  engineer  and  as  affording  plans  which 
can  be  amplified,  modified  or  shortened  to  meet  special  needs.  If 
more  complete  schemes  are  desired,  they  are  to  be  found  in  the 
article  by  Dr.  Joiiet  already  mentioned.  As  rocks  and  slags  have 
much  in  common  from  an  analytical  standpoint,  Dr.  Hillebrand's 
bulletin  on  rock  analysis  will  give  much  valuable  information. 


FLUE    GAS   ANALYSIS.  125 


CHAPTER    XVI. 

Flue  Gas  Analysis. 

Any  engineer  is  almost  certain  to  have  charge  of  some  kind  of 
a  power  plant,  usually  one  where  the  heat  of  combustion  of  coal 
is  the  source  of  power  ;  in  order  to  ascertain  the  efficiency  at  which 
the  plant  is  run,  he  must  know  at  least  the  analysis,  better  also,  the 
calorific  power,  of  the  coal,  and  the  composition  of  the  flue  gas 
and  the  ash  —  the  results  of  combustion. 

The  examination  of  the  ash  is  for  unburned  carbon  and  requires 
no  additional  description.*  The  determinations  required  in  the 
flue  gas  are  carbon  dioxide,  carbon  monoxide,  oxygen  and  nitro- 
gen ;  the  first  two  are  of  the  greatest  importance,  as  the  higher 
the  carbon  dioxide  and  the  lower  the  monoxide,  the  more  efficient 
is  the  combustion.  If  this  is  obtained  by  the  introduction  of  an 
excessive  quantity  of  air,  both  the  carbon  dioxide  and  monoxide 
will  be  low. 

All  that  is  required  of  the  engineer  is  a  knowledge  of  how  to 
determine  these  four  important  constituents,  really  only  three  for 
the  nitrogen  is  determined  by  difference,  in  order  to  ascertain 
whether  the  fuel  is  being  used  economically.  This  is  obtained 
more  satisfactorily  by  a  number  of  analyses  at  frequent  intervals, 
each  made  with  rapidity,  than  by  one  analysis  made  with  all  the 
precautions  and  corrections,  on  account  of  the  variations  in  the 
composition  of  the  gas  due  to  additions  of  fresh  fuel,  changing  of 
draughts,  etc.  Therefore  no  mention  will  be  made  here  of  the  so- 
called  "  exact "  gas  analysis,  where  all  the  measurements  are  made 
over  mercury  and  allowance  made  for  changes  in  temperature, 
barometer,  etc.,  except  to  refer  the  reader  to  Hempel's  Gas  Analy- 
sis, recently  translated  by  Prof.  Dennis.  We  need  only  consider 
the  most  simple  application  of  "  technical  "  gas  analysis. 

Gas  analysis  is  a  branch  of  volumetric  analysis  and  the  results 
are  always  expressed  in  percentage  by  volume.  Now,  as  the  vari- 
ation of  volume  of  all  gases  for  temperature  and  pressure  is  the 
same,  the  percentage  by  volume  at  any  given  temperature  and 
pressure  will  be  the  same  as  under  the  standard  conditions,  O°C. 

*  See  coal  analysis. 


126  QUANTITATIVE   ANALYSIS. 

and  760  mm,  It  is  therefore  only  when  some  particular  con- 
stituent is  absorbed  and  afterwards  determined  gravimetrically  or 
by  titration,  that  it  is  necessary  in  the  "  technical  "  analysis  to  ap- 
ply the  corrections  for  temperature,  pressure  and  tension  of  aque- 
ous vapor.  However,  variations  of  temperature  or  of  pressure 
must  be  most  carefully  guarded  against  while  the  analysis  is  in 
progress,  as  these  would  vitiate  the  results.  Whenever  possible, 
the  analysis  is  conducted  in  a  room  of  even  temperature,  prefer- 
ably with  a  northern  exposure.  All  measurements  are  made  at 
the  atmospheric  pressure  and  over  water  which  has  been  previ- 
ously saturated  with  a  gas  similar  to  that  under  examination. 

If  the  temperature  remains  constant  the  tension  of  aqueous 
vapor  is  also  constant,  and  when  the  analysis  is  conducted  rapidly 
the  variations  of  the  atmospheric  pressure  are  not  likely  to  affect 
the  results  seriously.  So  as  these  conditions  are  practically  con- 
stant, the  results  expressed  in  percentage  by  volume  will  agree 
within  an  allowable  error  of  say  o.  I  per  cent,  of  the  results  calcu- 
lated to  the  standard  conditions.  Unless  there  is  a  sudden  bar- 
ometric change  or  by  carelessness  the  gas  becomes  changed  in 
temperature,  the  error  is  likely  to  be  less  than  the  inaccuracy  in 
reading  the  volumes. 

Saturating  the  water  over  which  the  gas  is  measured  or  kept, 
and  also  the  reagents,  with  the  gases  present,  which  are  not  to  be 
absorbed  by  this  particular  reagent,  deserves  special  emphasis. 
All  gases  are  soluble  in  water]  to  some  extent  and  as  carbon 
dioxide  is  soluble  to  the  extent  of  about  one  volume  of  the  gas 
to  one  volume  of  water,  the  error  due  to  this  cause  may  be  great. 
The  saturation  is  easily  accomplished  by  running  through  one  or 
two  analyses  of  the  gas,  after  the  apparatus  has  been  filled  with 
water,  reagents,  etc.,  before  making  the  analysis,  the  results  of 
which  are  to  be  used. 

The  Orsat  apparatus  is  the  most  convenient  for  flue  gas  analysis, 
as  it  is  compact  and  portable.*  It  is  assumed  in  these  notes  that 
this  form  of  apparatus  is  to  be  used. 

REAGENTS. 

Carbon  dioxide  is  removed  by  a  strong  solution  of  potassium  hy- 
dioxide,  500  grams  of  commercial  caustic  potash  to  a  liter  of 

*  A  description  of  this  apparatus  can  be  found  in  the  text-books  given  at  the  end 
of  this  chapter  or  in  the  circulars  of  the  dealers  in  chemical  apparatus. 


FLUE    GAS   ANALYSIS.  127 

water,  each  cubic  centimeter  of  this  reagent  absorbs  about  40  c.c. 
of  carbon  dioxide.  This  is  the  first  reagent  used  with  the  flue  gas. 

Oxygen  is  absorbed  by  an  alkaline  pyrogallate  solution,  made 
by  dissolving  (as  far  as  possible  out  of  contact  with  the  air)  5 
grams  of  pyrogallol,  C6H3(OH)3,  in  100  c.c.  of  the  potassium  hy- 
droxide given  above.  Pyrogallol  or,  as  it  is  frequently  termed, 
pyrogallic  acid,  is  a  triatomic  phenol,  when  dissolved  in  potassium 
hydroxide  the  three  hydrogens  of  the  hydroxyl  groups  are  re- 
placed by  potassium  atoms.  When  oxygen  is  absorbed  no  definite 
reaction  takes  place,  but  acetic  acid,  and  brown  humus-like  sub- 
stances are  formed.  The  reagent  will  be  quickly  exhausted  if  ex- 
posed to  the  air  ;  each  c.c.  absorbs  about  2  c.c.  of  oxygen.  This 
is  the  second  reagent  used  in  the  flue  gas  analysis  ;  it  is  evident 
that  as  it  contains  an  enormous  excess  of  caustic  alkali  it  would, 
if  used  first,  absorb  carbon  dioxide  as  well  as  oxygen. 

Carbon  monoxide  is  absorbed  by  a  hydrochloric  acid  solution  of 
cuprous  chloride,  which  is  made  as  follows  :*  Cover  the  bottom 
of  a  large  wide-mouthed  bottle  with  black  oxide  of  copper,  not 
necessarily  pure,  to  a  depth  of  about  half  an  inch  ;  fill  nearly  full 
with  hydrochloric  acid  i.i  sp.  gr.;  add  about  a  hundred  pieces  of 
stout  copper  wire,  cut  in  lengths  of  about  six  inches,  so  that  they 
shall  reach  from  the  bottom  to  the  top  of  the  bottle  ;  allow  to 
stand,  shaking  occasionally,  till  the  solution  is  colorless  ;  then 
withdraw  for  use.  The  action  is  that  the  cupric  oxide  dissolves 
in  the  hydrochloric  acid  giving  cupric  chloride,  this  in  turn  dis- 
solves copper  from  the  wires  forming  cuprous  chloride,  the  reagent 
desired. 

The  wires  keep  up  the  strength  of  the  solution  and  reduce  any 
cupric  chloride  formed  by  the  air  back  to  cuprous.  The  solution 
should  be  nearly  colorless  when  used.  The  amount  of  carbon  mon- 
oxide absorbed  per  c.c.  is  given  variously  by  different  authorities,  but 
it  is  safe  to  assume  that  it  will  absorb  an  equal  volume  of  carbon 
monoxide.  The  reaction  is  supposed  to  result  in  the  formation  of 
an  unstable  addition  product,  Cu2Cl2.CO.  As  there  is  usually 
only  a  few  tenths  of  a  per  cent,  of  carbon  monoxide  in  flue  gas, 
this  reagent  will  last  for  some  time  if  protected  from  oxidation  or 
if  kept  in  contact  with  metallic  copper.  This  is  the  third  and  last 
reagent  used  with  flue  gas. 

*  Gill,  *'  Gas  Analysis  for  Engineers,"  p.  34. 


128  QUANTITATIVE   ANALYSIS. 

SAMPLING. 

The  sample  should  be  taken  as  close  as  possible  to  the  point 
where  the  flame  ends  and  at  the  place  in  the  flue  of  smallest  cross- 
section,  to  prevent  admixture  of  air  and  to  get  a  sample  of  the  gas 
which  is  really  the  result  of  the  combustion  in  progress  when  the 
sample  is  obtained.  Tubes  are  usually  inserted  in  the  wall  of  the 
chimney  or  other  flue,  which  should  penetrate  to  the  center  and 
contain  asbestos  to  filter  out  dust,  etc.  They  may  be  made  of 
hard  glass  (combustion  tubing),  porcelain  or  metal  depending  on 
the  temperature.  Iron  tubes  are,  however,  obectionable  as  they 
become  coated  with  oxide,  which  is  reduced  by  the  carbon  mon- 
oxide in  the  gas  with  an  increase  in  the  amount  of  carbon  dioxide. 

The  end  of  the  tube  is  provided  with  a  cork  or  rubber  stopper 
through  which  passes  a  smaller  glass  tube,  which  is  connected  by  a 
short  rubber  tube  with  the  sample  tube.  Many  convenient  forms 
of  apparatus  for  samples  of  gas  can  be  had  from  the  dealers,  but 
all  that  is  necessary  is  a  large  pipette,  200-250  c.c.,  provided 
with  a  short  piece  of  rubber  tubing  at  both  ends  and  two  clamps. 

As  the  draught  of  the  chimney  must  be  overcome  in  taking  the 
sample,  some  form  of  aspirator  is  needed.  Water  pumps  are  con- 
venient when  water  pressure  is  at  hand,  but  a  simple  and  service- 
able pump  *  can  be  made  by  reversing  the  valve  of  an  ordinary 
large-sized  bicycle  pump. 

The  aspirator  is  attached  to  the  sample  tube  and  the  flue  gases 
drawn  through  for  several  minutes  to  displace  the  air  which  fills 
the  tube  and  connections  ;  then  the  ends  of  the  sample  tube  are 
closed  (by  the  clamps  on  the  rubber  tubes)  and  the  sample  is 
taken  to  the  Orsat  apparatus. 

ANALYSIS. 

The  Orsat  apparatus  consists  essentially  of  three  pipettes  con- 
taining the  reagents  already  described  and  a  measuring  tube  grad- 
uated from  o  to  100  c.c.  in  tenths,  provided  with  a  levelling 
bottle,  so  that  the  pressure  of  the  gas  can  be  made  equal  to  that 
of  the  atmosphere.  The  measuring  tube  and  connections  are 
filled  with  water  by  turning  a  stop-cock  and  raising  the  levelling 
bottle ;  then  the  tube  containing  the  sample  is  connected  by  one 
end,  while  the  other  is  placed  under  water,  to  prevent  admixture 
of  air  when  the  sample  of  gas  is  removed  ;  the  connections  are 

*  Devised  by  Irving  Langmuir. 


FLUE    GAS   ANALYSIS.  129 

opened  and  by  lowering  the  levelling  bottle  a  little  more  than  100 
c.c.  of  the  flue  gas  is  drawn  into  the  measuring  tube  ;  the  sample 
tube  is  then  closed  and  disconnected  and  the  excess  of  flue  gas 
above  100  c.c.  driven  out  by  raising  the  levelling  bottle  so  that  the 
liquid  in  the  measuring  tube  and  in  the  bottle  shall  coincide  with 
the  loo-c.c.  mark.  Then  the  stop-cock  is  turned  to  prevent  the 
escape  of  gas  and  the  analysis  is  begun.  The  gas  is  run  into  the  first 
pipette,  containing  potassium  hydroxide.  By  raising  the  levelling 
bottle,  the  gas  displaces  the  alkali  solution,  which  passes  into  the 
rear  portion  of  the  pipette,  displacing  in  turn  air  which  expands  a 
rubber  bag.  In  this  way  the  reagents  are  kept  from  contact  with 
the  atmosphere.  In  the  pipettes  are  a  number  of  glass  rods ; 
when  the  reagent  is  displaced  these  rods  remain  wet  and  so  give 
a  large  surface  for  the  absorption  of  carbon  dioxide  from  the  flue 
gas.  After  three  minutes  the  gas  is  drawn  back  into  the  measur- 
ing tube,  care  being  taken  that  the  reagent  comes  back  to  exactly 
the  point  at  which  it  stood  before  on  the  capillary  tube  connecting 
with  the  pipette  ;  and  the  gas  is  remeasured  at  the  atmospheric 
pressure.  The  decrease  in  volume  gives  the  percentage  of  carbon 
dioxide.  In  order  to  ensure  the  complete  absorption  of  any  con- 
stituent it  is  well  to  run  the  gas  over  again  into  the  pipette  for 
three  minutes  and  then  back  and  take  a  second  reading ;  if  more 
than  two  treatments  are  required,  the  reagent  is  becoming  ex- 
hausted and  should  be  renewed.  When  the  carbon  dioxide  has 
been  completely  removed,  the  gas  is  run  into  the  second  pipette, 
containing  alkaline  pyrogallate,  and  the  oxygen  removed  in  the 
same  way.  As  this  reagent  is  likely  to  become  weakened  in  a 
very  short  time  several  treatments  are  often  necessary.  After  the 
oxygen  has  been  removed  and  the  second  decrease  in  volume 
noted,  the  gas  is  run  over  into  the  third  pipette  containing  cuprous 
chloride,  for  the  removal  of  carbon  monoxide ;  then  back  and 
the  final  reading  taken.  The  residual  gas  is  considered  nitrogen. 
Great  care  should  be  taken  when  making  the  readings  to  have 
the  level  in  the  levelling  bottle  and  the  measuring  tube  the  same, 
so  that  the  gas  is  under  exactly  atmospheric  pressure  each  time. 

RESULTS. 

While  it  is  not  the  province  of  analytical  chemistry  to  discuss 
the  results,  it  is  to  be  expected  that  the  carbon  dioxide  will  be 
from  5-12  per  cent,  the  carbon  monoxide  0.0-0.4  Per  cent.,  the 


130  QUANTITATIVE   ANALYSIS. 

oxygen  together  with  the  carbon  dioxide  should  usually  be  be- 
tween 20  and  21  per  cent.,  and  the  remainder  nitrogen. 

While  there  is  some  variation  in  the  percentage  of  oxygen  in  the 
air  in  different  places,  country  and  city,  streets  and  parks,  it  is  very 
slight,  and  20.9  per  cent,  is  very  close  to  the  correct  percentage. 
Now  if  we  burn  carbon  in  air  completely  to  carbon  dioxide,  as  the 
volume  of  carbon  dioxide  is  equal  to  the  volume  of  oxygen  used, 
according  to  Avogadro's  law,  the  sum  of  the  percentages  of  oxy- 
gen and  carbon  dioxide  should  equal  that  of  the  oxygen  in  the  air, 
i.  c.,  20.9  per  cent.  But  it  often  happens  in  the  analysis  of  flue 
gas  that  the  sum  of  these  two  does  not  equal  20.9  per  cent.;  for 
if  any  carbon  monoxide  is  produced  we  get  two  volumes  of  carbon 
monoxide  for  each  volume  of  oxygen,  hence  the  percentage  of 
nitrogen  is  diminished  ;  on  the  other  hand  if  hydrocarbons  such  as 
methane,  etc.,  are  present,  from  bituminous  coal,  we  get  one  vol- 
ume of  carbon  dioxide  from  two  volumes  of  oxygen,  as  the  water 
condenses,  and  therefore  an  increase  in  the  percentage  of  nitrogen 
over  that  in  the  air.  (See  also  Calculations  of  Analytical  Chem- 
istry, Chapter  VIII.) 

For  further  information  on  flue  gas  analysis  the  reader  is  referred 
to  Gills'  "  Gas  and  Fuel  Analysis  for  Engineers  "  ;  Stillman's  "  En- 
gineering Chemistry,"  and  Blair's  "  Chemical  Analysis  of  Iron." 
For  a  complete  discussion  of  gas  analysis  see  Hempel's  "  Gas 
Analysis  "  translated  by  Dennis,  and  Winkler's  "  Technical  Gas 
Analysis,"  translated  and  enlarged  by  Lunge. 


REFERENCES    TO    ADDITIONAL    ANALYSIS.     131 


CHAPTER  XVII. 

References  to  Additional  Analysis. 

The  last  chapter  concluded  the  descriptions  of  the  analyses  re- 
quired of  the  mining  engineers  at  Columbia  University,  but  not 
all  those  frequently  needed  in  practice  ;  so  this  final  chapter  will 
contain  references  to  recent  reliable  descriptions  of  a  number  of 
additional  analyses  which  are  often  required  of  mining  engineers, 
metallurgists  or  chemists. 

The  following  abbreviations  will  be  used  : 

Journal  of  the  American  Chemical  Society,  J.  Am.  C.  S. 

Transactions  of  the  American  Institute  of  Mining  Engineers, 
T.  A.  /.  M.  E. 

School  of  Mines  Quarterly,  S.  of  M.  Qly. 

Chemical  News,  C.  N. 

Zeitschriftfur  Analytische  Chemie,  Z.  A.  C. 

Zeitschrift  fur  Anorganische  Chemie,  Z.  Anorg.  C. 

Zeitschriftfur  Angewandte  Chemie,  Z.  Angew.  C. 

Journal  of  the  Society  of  Chemical  Industry,  J.  S.  C.  I. 

Engineering  and  Mining  Journal,  E.  &  M.  J. 

Alkalimetry  and  Acidimetry. 

BUTTON'S  Volumetric  Analysis,  Eighth  Edition. 

MOHR'S  Lehrbuch  der  Titrirmethoden,  Seventh  Edition.  Revised 
by  Classen. 

JAMES  AND  RITCHEY.  Analyses  Required  for  an  Electrolytic  Al- 
kali Works.  J.  Am.  C.  S.,  24,  469,  1902. 

Review  of  Alkali  Determinations.     Z.  A.  C,  37,  684,  1898. 

NORTH  AND  LEE.  On  the  Estimation  of  Alkaline  Hydrate  or  Bi- 
carbonate in  the  Presence  of  Monocarbonate.  J.  S.  C.  I.,  21, 
322,  1902. 

RIEGLER.  Zur  Titerstellung  sowie  zur  Bestimmung  kaustischer 
und  kohlensaure  Alkalien.  Z.  A.  C.,  38,  250,  1899. 

Review.     Standardizing  Acid  and  Alkali.     Z.  A.  C.,  40,  411,  1901. 

MARSHALL.  Preparation  of  Standard  Solutions  of  Sulphuric  Acid. 
J.  S.  C.  I.,  18,  5,  1899. 

Alkalies  in  Feldspar,  Rock  or  Slag. 
See  Hillebrand,  Bulletin  176,  U.  S.  Geological  Survey. 


132  QUANTITATIVE   ANALYSIS. 

Alloys. 

SACK.     Bibliographic  der  Metalllegierungen.     Z.  Anorg.  C.,   35, 
249,  1903. 

Type  Metals y  Bearing  Metals,  Etc. 

ANDREWS.     On  the  Analysis  of  Alloys  of  Tin,  Lead,  Antimony 

and  Arsenic.     J.  Am.  C.  S.,  17,  869,  1895. 
GARRIGUES.     Alloys  for  Metal  Bearings.     J.  Am.  C.  S.,  19,  934, 

1897. 
WALTERS    AND    AFFELDER.     Analysis   of  Bronzes    and    Bearing 

Metals.     J.  Am.  C.  S.,  25,  632,  1903. 
HERZ.     Trennung  von  Antimon  und  Zinn  mittels  Oxalsaure.      Z. 

Anorg.  C,  37,  I,  1903. 

Bronze,  Brass,  German  Silver. 

CAIRNS.     Quantitative  Analysis. 

TREADWELL.     Arialytische  Chemie,   Vol.  II.    (now  translated  by 

Hall). 

SMITH.     Electrochemical  Analysis. 
RIBAN.     Traite  d'analyse  chimique  par  1'electrolyse. 

Bismuth. 
RIEDERER.     Volumetric  Determination  of  Bismuth  as  Molybdate 

and  its  Separation  from  Copper.     J.  Am.   C.  S.,  XXV.,  907, 

1903. 
WIMMENAUR.     Electrolytic   Estimation  of  Bismuth.     Z.   Anorg. 

C.,  27,  I,  1901. 
CLARK.     Separation  of  Bismuth  from  Lead.     J.  S.  C.  I.,  19,  26, 

1900. 
Bismuth  in  Pig  Lead.     Furman's  Assaying,  p.  163. 

Boric  Acid  and  Borax. 
THADDEEFF.     Bestimung  der  Borsaure  als  Borfluokalium.     Z.  A. 

C,  36,  568,  1897. 
GLADDING.     Boric  Acid  Determination.     J.  Am.  C.  S.,  20,  288, 

1898. 

SARGENT.     Determination  of  Boric  Acid  in  Tourmaline.     J.  Am. 
C.  S.,  21,  859,  1899. 

Cadmium. 

BIEWEND.     Ueber  den  Kadmium  gehalt  der  Zinkerze.     Berg  und 
Huttenmannische  Z.,  61,  401. 


REFERENCES    TO    ADDITIONAL   ANALYSIS.     133 

MILLER  AND  PAGE.     Quantitative  Determination  of  Cadmium.    S. 
of  M.  Quarterly,  22,  391,  1901. 

Calorific  Power  of  Fuel. 
ATWATER  AND  SNELL.     Description  of  a  Bomb  Calorimeter  and 

Method  of  its  Use.     J.  Am.  C.  S.,  25,  659,  1903. 
PARR.     The  Peroxide  Calorimeter  as  Applied  to  European  Coals 

and  Petroleum.     J.  Am.  C.  S.,  24,  167,  1902. 
LUNGE.     Ueber  das  verfahren  von  Parr  zur  Bestimmung  des  Heiz- 

werthes  von  Brennstoffen.     Z.  Angew.  C.,  14,  793,  1901. 
KENT.     Calorific    Value  of  American  Coals.     T.  A.   I.   M.   E., 

November,  1897. 

PARR.     Coal  Calorimeter.     J.  Am.  C.  S.,  22,  646,  1900. 
NOYES,  W.  A.      Determination  of  the  Heating  Effect  of  Coals. 

J.  Am.  C.  S.,  17,  843,  1895. 

Cement. 

STILLMAN'S  Engineering  Chemistry. 
MEADE.     Chemical  and  Physical  Examination  of  Portland  Cement, 

1901. 

CANDLOT.     Ciments  et  Chaux  Hydrauliques.      1898,  Paris. 
LUNGE.     Chemische-Technische  Untersuchungs  Methoden.    Vol. 

i>  PP.  599-677. 
HILLEBRAND  AND  RICHARDSON.    Report  on  Analysis  of  Materials 

for  Portland  Cement  Industry.     J.  S.  C.  I.,  21,  12,  1902. 
HILLEBRAND.     Critical  Review  of  Certain  Cement  Analyses,  etc. 

J.  Am.  C.  S.,  25,  1180,  1903. 

Chlorates,  Etc. 
SUTTON.     Volumetric  Analysis,  p.  186,  etc. 

Chromium. 

CAIRNS.     Quantitative  Analysis. 
BLAIR.     Chemical  Analysis  of  Iron. 
McKENNA.     Complete  Analysis  of  Chrome  Ore.     Proc.  Eng.  Soc. 

of  Western  Pa.,  63,  180,  1897. 
MAHON.     Chromium  in  Steel.     J.  Am.  C.  S.,  21,  1057,  1899. 

Cobalt. 
CLASSEN.     Ausgewahlte  Methoden,  p  425. 


134  QUANTITATIVE   ANALYSIS. 

Cyanide  Solutions. 

EISSLER.     The  Cyanide  Process  for  the  Extraction  of  Gold,  and 

other  books  on  Gold  Metallurgy,  Rose,  etc. 
GREEN.     Testing  Cyanide  Solutions  Containing  Zinc.     Institute  of 

Mining  and  Metallurgy,  October  17,  1901. 
CHRISTY.     Electromotive  Force  of  Metals  in  Cyanide  Solutions. 

T.  A.  I.  M.  E.,  30,  864. 

Review  of  Methods  of  Analysis.     Z.  A.  C.,  38,  792,  1899. 
SHARWOOD.     Notes  on  the  Estimation  of  Cyanogen,  etc.     J.  Am. 

C.  S.,  19,  400,  1897. 

Copper. 

FRESENIUS.       Hampe's  method.      Quantitative  Analysis,  English 

Edition,    1900,  page  405. 
KELLER.      On  the  Analysis  of  American   Refined   Copper.      J. 

Am.  C.  S.,  16,  785,  1894. 
HOLLARD.      Analysis    of    Commerical    Copper   by    Electrolytic 

Methods.     Bulletin  Soc.  Chimique,  23,  292,  1900. 
ULKE.      Copper  Assaying  and  Analysis,  Commercial    Methods. 

E.  and  M.  J.,  December  16,  1899. 
Review  of  Methods.     Z.  A.  C.,  37,  120,  1898. 

Fluorine. 

JANNASCH.     Praktische  Leitfaden  der  Gewichts  Analyse,  p.  267. 
STAHL.     Analysis  of  Commercial  Hydrofluoric  Acid.     J.  Am.  C. 
S.,  18,  415. 

Indicators. 

SUTTON.     Volumetric  Analysis. 

Review  of  Indicators,  Z.  A.  C.,  42,  304,  1903. 

LUNGE.     Bericht  der  Indikatoren-Kommission.     Z.  Angew.  C.,  1 6, 

H5,  1903- 

GLASER.     Ueber  Indicatoren.     Z.  A.  C.,  41,   36,  1902;  also  38, 
273,  1899. 

Lead.     Refined  Lead. 

CAIRNS.     Quantitative  Analysis. 

Review  of  Methods,  Z.  A.  C.,  42,  628,  1903. 

Lithium. 

JANNASCH.     Gewichtsanalyse. 

WALLER.      Bei  der  Bestimmung  des  Lithiums.     Z.  A.  C.,  36,  513, 
1897. 


REFERENCES    TO    ADDITIONAL   ANALYSIS.     135 

Mercury. 

FURMAN.     Manual  of  Assaying. 

CHISM.     Assay  for  Mercury.     E.  &  M.  J.,  66,  86. 

SMITH  AND  WALLACE.  Electrolytic  Estimation  of  Mercury.  J. 
Am.  C.  S.,  1 8,  169,  1896. 

RISING  AND  LENHER.  An  Electrolytic  Method  for  the  Determi- 
nation of  Mercury  in  Cinnabar.  J.  Am.  C.  S.,  18,  96,  1896. 

PRETZFELD.  Gravimetric  Estimation  of  Mercury  and  its  Separa- 
tion from  Arsenic,  Antimony  and  Copper.  J.  Am.  C.  S.,  XXV., 
198,  1903. 

Molybdenum. 

KOPP.     Molybdenum  in  Steel.     J.  Am.  C.  S.,  24,  186,  1902. 
AUCHY.     Molybdenum  in  Steel.     J.  Am.  C.  S.,  24,  273,  1902. 

Nickel. 
SARGENT.     Determination  of  Nickel  in  Nickel  Steel.     J.  Am.  C. 

S.,  21,  854,  1899. 
EDWARDS.     Nickel  Assay.    New  Caledonia.    E.  &  M.  J.,  May  28, 

1898. 
LANGMUIR.      Nickel  in  Nickel  Ores.      J.  Am.   C.  S.,   22,    102, 

1900. 

HERZ.     Nickel  Sulphide,  etc.     Z.  Anorg.  C.,  28,  342,  1901. 
TAGGART.     Electrolytic   Precipitation  of  Nickel   from  Phosphate 

Solutions.     J.  Am.  C.  S.,  25,  1039,  19°3> 

Oils. 

GILL.     Oil  Analysis. 

ALLEN.     Commercial  Organic  Analysis,  Vol.  II. 
LEWKOWITSCH.     Chemical  Analysis  of  Oils,  Fats  and  Waxes. 

Paint. 

ELLIS.     White  Paint  Analysis  (Evanston,  111.). 
THOMPSON.     Analysis  of  WThite  Paint.     J.  S.  C.  I.,  15,  432  and 

791,  1896. 
GNEHM.     Unorganische  Farbstoffe  in    Lunge's    Chemisch-Tech- 

nische  Untersuchungs  Methoden,  Vol.  II.,  pp.  765—804. 

Phosphates,  Etc. 

WYATT.     Phosphates  of  America. 

CHATARD.  Phosphate  Chemistry  as  it  Concerns  the  Miner.  T. 
A.  I.  M.  E.,  21,  160. 


136  QUANTITATIVE   ANALYSIS. 

GLADDING.     Determination  of  Iron  Oxide  and  Alumina  in  Phos- 
phate Rock.     J.  Am.  C.  S.,  18,  717  and  721,  1896. 
Bulletins  of  U.  S.  Dept.  of  Agriculture. 

Platinum  Metals. 

CLASSEN.     Ausgewahlte     Methoden    der  Analytischen     Chemie. 

Vol.  I,  1901.  ' 
LEIDIE  AND  QUENNESSEN.     Estimation  of  Platinum  and  Iridium  in 

Platinum  Ores.     C.  N.,  84,  216,  1901. 
RICHARDS.     Estimation  of  Platinum,  Gold  and  Silver  in  Alloys. 

Analyst,  27,  266,  1902. 
WILEY.     Recovery  of  Waste  Platinum  Chloride.     J.  Am.   C.  S., 

19,  258,  1897. 

Separations. 

In  general  see  the  works  of  Fresenius,  Classen  and  Treadwell  ; 
for  the  halogens  and  alkaline  earths  see  Jannasch's  Gewichts- 
analyse. 

Sulphur  in  Pyrites. 

LUNGE.     On  the '"Estimation  of  Sulphur  in  Pyrites.     J.  Am.  C.  S., 

17,  181,  1895. 
GLADDING.     J.  Am.  C.  S.,  16,  403,  1894. 

Tin. 

Review  on  Tin,  Antimony  and  Arsenic.     Z.  A.  C.,  38,  307-323, 

1899. 

WELLS.     Analysis  of  Tin  Ore.     S.  of  M.  Qly,  12,  295,  1891. 
MILLER.     Assay  of  Tin  Ore.     S.  of  M.  Qly.,  13,  369,  1892. 

Thorium  and  Other  "Hydroxide"  Elements. 

Treadwell's    Analytical    Chemistry   and    Classen's    Ausgewahlte 
Methoden. 

Titanium. 

Review  of  the  Determination  of  Titanium.     Z.  A.   C.,  40,  799, 

1901. 
BASKERVILLE.     On  the  Analysis  of  Titaniferous  Iron  Ores.     J.  S. 

C.  L,  19,  419,  1900- 
POPE.     Investigation  of  Magnetic  Iron  Ores  from  Eastern  Ontario. 

T.  A.  I.  M.  E.,  29,  372,  1899. 
BAIN.     The  Estimation  of  Titanium.       J.  Am.   C.  S.,  25,  1073, 

1903. 


REFERENCES    TO    ADDITIONAL   ANALYSIS.     13? 

Tungsten. 
BORNTRAGER.     Rasche  Wolframprobe  und  Analyse  von  Wolfram- 

erzen,  etc.     Z.  A.  C,  39,  361,  1900. 
Tungsten  in  Steel :  Blair;  McKenna,  C.  N.,  67,  1900;  Auchy,  J. 

Am.  C.  S.,  21,  239,  1899. 

Uranium. 
KERN.     Quantitative  Separation  and  Determination  of  Uranium. 

J.  Am.  C.  S.,  23,  685-726,  1901. 

FRITCHLE.     Analysis  of  Uranium  and  Vanadium  Ores.     E.   & 
M.  J.,  Nov.  10,  1900. 

Water. 

MASON.     Examination  of  Water.      1901. 
STILLMAN.     Engineering  Chemistry,  pp.  42-97.     1900. 

For  those  determinations,  to  which  no  references  are  given,  see 
the  standard  text-books  on  quantitative  analysis,  among  these : 
Classen's  "  Ausgewahlte  Methoden  der  Analytischen  Chemie,  2 
vols.,  1901  and  1903,  Treadwell's  "  Analytische  Chemie,"  vol.  I, 
qualitative,  vol.  2,  quantitative,  recently  translated  by  Hall,  and 
Fresenius'  "  Quantitative  Chemical  Analysis  "  translated  by  Groves 
(English),  1900,  or  by  Cohn  (American),  1903,  are  the  best;  and 
also  Waller's  abstracts  on  Analytical  Chemistry  which  are  to  be 
found  in  the  SCHOOL  OF  MINES  QUARTERLY. 


Catalogue    of  the   Scientific    Publications 
and  Importations  of  D.  Van  JVbstrand  Com- 

pany,  23  Murray  Street  and  27    Warren  Street,  New 
York. 

A.  B.  C.  CODE.     (See  Clausen-Thue.) 

ABBOTT,  A.  V.    The  Electrical  Transmission  of  Ener- 

gy.     A  Manual  for  the  Design  of  Electrical  Circuits.      Ihird  Edi- 
tion, Thoroughly  Revised.    Fully  illustrated.     8vo,  cloth  .....  $4  50 

ABBOT,   Gen'l  HENRY  L.      The  Defence  of  the  Sea- 

coast  of   the  United  States.     Lectures  delivered  before  the  U.   S. 
Naval  War  College.     8vo,  red  cloth  ...................  .......  $2.00 

ADAM,   P.     Practical    Bookbinding.     With   Illustra- 

tions and  Figures.     Translated  from  the  German  by  Thomas  E.  Maw. 
8vo,  cloth,  illustrated 


ADAMS,  J.  W.    Sewers  and  Drains  for  Populous  Dis- 

tricts. Embracing  Rules  and  Formulas  for  the  dimensions  and  con- 
struction of  works  of  Sanitary  Engineers.  8vo,  cloth  ..........  $2.50 

ADDYMA.N,   FRANK    T.     Practical  X    Ray   Work. 

Part  I,  Historical.  Part  II,  Apparatus  and  its  Management.  Part 
III,  Practical  X  Bay  Work.  Illustrated  with  twelve  plates  from  Photo- 
graphs. 8vo,  cloth,  illustrated  ..........................  net,  $4.00 

A.  1  CODE.    (See  Clausen-Thue.) 

AIKMAN,  C.  M.,  Prof.      Manures  and  the  Principles 

of  Manuring.     8vo,  cloth  .....................................  $2.50 

ALEXANDER,  J.  H.  Universal  Dictionary  of  Weights 

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BEECH,  FRANKLIN.     Dyeing  of  Cotton  Fabrics.    A 

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BECKWITH,  ARTHUR.     Pottery.     Observations  on 

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BEGTRUP,  JULIUS,  M.  E.    The  Slide  Valve  and  its 

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BERNTHSEN,  A.    A  Text-Book  of  Organic  Chemistry. 

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BERTIN,  Li.  E.     Marine   Boilers :    Their   Construction 

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and  other  tables.  New  Edition.  8vo,  cloth $1.75 

CHARPENTIER,  PAUL.     Timber  ;  a  Comprehensive 

Study  of  Wood  in  all  its  Aspects  ;  Commercial  and  Botanical.  Show- 
ing the  Different  Applications  and  Uses  of  Timber  in  Various  Trades, 
etc.  Translated  into  English.  8vo,  cloth,  illustrated.  437  pp.. net,  $6.00 

CHAUVENET,  Prof.  W.     New  Method  of  Correcting 

Lunar  Distances,  and  Improved  Method  of  Finding  the  Error  and 
Kate  of  a  Chronometer,  by  Equal  Altitudes.  8vo,  cloth $2  00 

CHILD,  CHAS.  T.     The  How  and  Why  of  Electricity. 

A  Book  of  information  for  non-technical  readers,  treating  of  the 
Properties  of  Electricity,  and  how  it  is  generated,  handled,  controlled, 
measured  and  set  to  work.  Also  explaining  the  operation  of  Electri- 
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CHRISTIE,    W.   WALLACE.      Chimney  Design  and 

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tone illustrations  and  plates  of  famous  chimneys.  Second  edition, 
revised.  8vo,  cloth $3. 00 

Furnace    Draft  ;   its    Production   by    Mechanical 

Methods.  A  Handy  Eeference  Book,  with  figures  and  tables.  16mo, 
limp  cloth,  illustrated : $0.50 

Boiler- waters,  Scale  and  Corrosion In  Press 

CHURCH,  JOHN  A.    Notes  of  a  Metallurgical  Journey 

in  Europe.      8vo,  cloth $2.00 

CLAPPERTON,    GEO.      Practical    Paper-making ;    a 

Manual  for  Paper-makers  and  Owners  and  Managers  of  Paper  Mills, 
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trations reproduced  from  micro-photographs.  12mo,  cloth,  illus- 
trated  $2.50 

CLARK,   D.   KINNEAR,   C.E.      A  Manual  of  Rules, 

Tables  and  Data  for  Mechanical  Engineers.  Based  on  the  most  recent 
investigations.  Illustrated  with  numerous  diagrams.  1,012  pages. 

8vo,  cloth,     Sixth  Edition $5.00 

Half  morocco $7.50 

Fuel;  its  Combustion  and  Economy,  consisting  of 

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Williams ;  and  the  Economy  of  Fuel,  by  T.  S.  Prideaux.  With 
extensive  additions  in  recent  practice  in  the  Combustion  and  Economy 
of  Fuel,  Coal,  Coke,  Wood.  Peat,  Petroleum,  etc.  Fourth  Edition. 
12mo,  cloth $1.50 


10  D.  VAN  NOSTRAND  COMPANY'S 


CLARK,  D.  KINNEAR,  C.  E.  The  Mechanical  Engi- 
neer's Pocket  Book  of  Tables,  Formulae,  Rules  and  Data.  A  Handy 
Book  of  Reference  for  Daily  Use  in  Engineering  Practice.  16mo, 
morocco.  Fifth  edition,  carefully  revised  throughout $3.0 

Tramways ;  their  Construction  and  Working,  Em- 
bracing a  comprehensive  history  of  the  system,  with  accounts  of  the 
various  modes  of  traction,  a  description  of  the  varieties  of  rolling 
stock,  and  ample  details  of  Cost  and  Working  Expenses.  Second 
Edition.  Re-written  and  greatly  enlarged,  with  upivards  of  400 
illustrations.  Thick  8vo,  cloth $9  00 

CLARK,  JACOB  M.      A  new  System  of  Laying  Out 

Railway  Turn-outs  instantly,  by  inspection  from  tables.  12mo,  cloth. 
$1.00 

CLAUSEN-THUE,  W.  The  A  B  C  Universal  Com- 
mercial Electric  Telegraphic  Code ;  specially  adapted  for  the  use  of 
Financiers,  Merchants,  Ship-owners,  Brokers,  Agent,  etc.  Fourth 
Edition,  i  8vo,  cloth. $5.00 

Fifth  Edition  of  same $7.00 

The  Al  Universal  Commercial  Electric  Telegraphic 

Code.    Over  1240  pp.,  and  nearly  90,000  variations.    8vo,  cloth.. $7. 50 

CLEEMANN,   THOS.   M.      The  Railroad    Engineer's 

Practice.  Being  a  Short  but  Complete  Description  of  the  Duties  of 
the  Young  Engineer  in  the  Prelimary  and  Location  Surveys  and  in 
Construction.  4th  ed.,  revised  and  enlarged.  Illus.  12mo,  cloth  $1.50 

CLEVENGER,   S.   R.    A  Treatise  on  the  Method  of 

Government  Surveying  as  prescribed  by  the  U.  S.  Congress  and 
Commissioner  of  the  General  Land  Office,  with  complete  Mathe- 
matical, Astronomical  and  Practical  Instructions  for  the  use  of  the 
United  States  Surveyors  in  the  field.  16mo,  morocco $2.50 

CLOUTH,   F.    Rubber,    Gutta-Percha,  and   Balata. 

Translated  from  the  German  edition,  and  thoroughly  revised  and 
brought  up-to-date.  With  engravings  and  maps.  8vo,  cloth,  illus- 
trated  In  Press. 

COFFIN,  Prof.  J.  H.  C.  Navigation  and  Nautical  As- 
tronomy. Prepared  for  the  use  of  the  U.  S.  Naval  Academy.  New 
edition.  Revised  by  Commander  Charles  Belknap.  52  woodcut  illus- 
trations. 12mo,  cloth net,  $3.50 

COLE,  R.  S.,  M.  A.   A  Treatise  on  Photographic  Optics. 

Being  an  account  of  the  Principles  of  Optics,  so  far  as  they  apply  to 
Photography.  12mo,  cloth.  103 illustrationsand  folding  plates. $2. 50 

COLLINS,  JAS.  E.    The  Private  Book  of  Useful  Alloys 

and  Memoranda  for  Goldsmiths,  Jewelers,  etc.     18mo,  cloth 50 


SCIENTIFIC  PUBLICATIONS.  11 


COREY.  Water  Supply  Engineering.  Fully  illus- 
trated. 8vo,  cloth In  Press. 

COOPER,    W.   R.,   M.  A.      Primary  Batteries  ;    their 

Construction  and  Use.  With  numerous  figures  and  diagrams.  8vo, 
cloth,  illustrated net,  $4.00 

CORNWALL,  Prof.  H.  B.  Manual  of  Blow-pipe  An- 
alysis, Qualitative  and  Quantitative.  With  a  Complete  System  of 
Determinative  Mineralogy.  8vo,  cloth,  with  many  illustrations.  .$2. 50 

COWELL,   W.  B.      Pure  Air,   Ozone   and  Water;    a 

Practical  Treatise  of  their  Utilization  and  Value  in  Oil,  Grease,  Soap, 
Paint,  Glue  and  other  Industries.  With  tables  and  figures.  12mo, 
cloth,  illustrated net.  $2.00 

CRAIG,  B.  F.    Weights  and  Measures.    An  account  of 

the  Decimal  System,  with  Tables  of  Conversion  for  Commercial  and 
Scientific  Uses.  Square  32mo,  limp  cloth 50 

CROCKER,  F.  B.  Electric  Lighting.  A  Practical  Ex- 
position of  the  Art.  For  use  of  Engineers,  Students,  and  others  inter- 
ested in  the  Installation  or  Operation  of  Electrical  Plants.  Vol.  I. 
The  Generating  Plant.  Fourth  Edition,  revised.  8vo,  cloth,  illus- 
trated   $3.00 

Vol.  II.  Distributing  Systems  and  Lamps.  Second  edition.  8vo,  cl., 
illustrated $3.00 

CROCKER,  F.  B.,  and  S.  S.  WHEELER.  The  Practical 

Management  of  Dynamos  and  Motors.  Fifth  Edition,  (Eleventh 
thousand)  revised  and  enlarged.  With  a  special  chapter  by  H.  A. 
Foster.  12mo,  cloth,  illustrated , $1.00 

DAVIES,  E.  H.      Machinery  for  Metalliferous  Mines. 

A  Practical  Treatise  for  Mining  Engineers,  Metallurgists  and  Man- 
agers of  Mines.     With  upwards  of  400  illustrations.     Second  edition, 
rewritten  and  enlarged.     8vo,  cloth net  $8.00 

D.  C.     A  Treatise  on  Metalliferous  Minerals  and 

Mining.  Sixth  edition,  thoroughly  revised  and  much  enlarged  by 
his  son.  8vo,  cloth net,  $5.00 

MINING  MACHINERY...  ..In  Press. 


DAVIS,  C.,    and  B.    F.    BELL.     Ferro-Concrete ;    Its 

Varieties  and  Applications  in  Modern  Construction.  8vo,  cloth, 
illustrated In  Press. 

DAY,  CHARLES.     The  Indicator  and  its  Diagrams. 

With  Chapters  on  Engine  and  Boiler  Testing  ;  Including  a  Table  of 
Piston  Constants  compiled  by  W.  H.  Fowler.  12mo,  cloth.  125 
illustrations $2.00 


12  D.  VAN  NOSTEAND  COMPANY'S 


DENNY,  G.  A.     Deep-level  Mines  of  the  Rand,  and 

their  future  development,  considered  from  the  commercial  point  of 
view.  With  folding  plates,  diagrams  and  tables.  4to,  cloth,  illus- 
trated  ". net,  $10.00 

DERR,  W.   Li.    Block  Signal  Operation.    A  Practical 

Manual.     Oblong,  cloth.     Second  Edition $1.50 

DIBDIN,  W.  J.     Chemical  Technology ;  or,  Chemistry 

in  its  Application  to  Arts  and  Manufactures,  with  which  is  incorporated 
Eichardson  and  Watts'  Chemical  Technology.  Vol.  IV.  Electric 
Lighting,  by  A.  G.  Cooke,  M.  A.  ;  Photometry,  by  W.  J.  Dibdin,F. 
I.  C.  With  tables,  diagrams,  figures  aud  plates.  8vo,  cloth,  illus- 
trated, 378  pages net.  $3.50 

Purification  of  Sewage  and  Water.    With  Tables, 

engravings,  and  folding  plates.     8vo,  cloth,  illustrated $6.50 

DIETERICH,    KARL.      Analysis  of  Resins,  Balsams 

and  Gum  Eesins  ;  their  Chemistry  and  Pharmacognosis.  For  the  use 
of  the  Scientific  and  Technical  Research  Chemist.  With  a  Bibliog- 
raphy. Translated  from  the  German,  by  Chas.  Salter.  8vo,  cloth. 
net,  $3.00 

DIXON,  D.  B.      The  Machinist's  and  Steam  Engineer's 

Practical  Calculator.  A  Compilation  of  Useful  Eules  and  Problems 
arithmetically  •  solved,  together  with  General  Information  applicable 
to  Shop-Tools,  Mill-Gearing,  Pulleys  and  Shafts,  Steam-Boilers  and 
Engines.  Embracing  valuable  Tables  and  Instruction  in  Screw-cutting, 
Valve  and  Link  Motion,  etc.  Third  edition.  16mo,  full  morocco, 
pocket  form $1.25 

DODD,   GEO.      Dictionary  of   Manufactures,  Mining, 

Machinery,  and  the  Industrial  Arts.     12mo,  cloth $1.50 

DORR,  B.  F.    The  Surveyor's  Guide  and  Pocket  Table 

Book.  Fifth  Edition.  thoroughly  revised  and  greatly  extended. 
With  a  second  appendix  up  to  date.  16mo,  morocco  flaps $2.00 

DRAPER,  C.  H.    An  Elementary  Text  Book  of  Light, 

Heat  and  Sound,  with  Numerous  Examples.  Fourth  edition.  12mo, 
cloth.  Illustrated $1.00 

Heat   and   the   Principles    of  Thermo-Dynamics. 

With  many  illustrations  and  numerical  examples.    12mo,  cloth.  .$1.50 

DYSON,  S.  S.     Practical  Testing  of  Raw  Materials; 

A  Concise  Hand-book  for  Manufacturers,  Merchants,  and  Users  of 
Chemicals,  Oils,  Fuels,  Gas  Residuals,  and  By- Products,  and  Paper- 
Making  Materials,  with  Chapters  on  Water  Analysis  and  the  Testing 
of  Trade  Effluents .  8vo,  cl. ,  ill. ,  177  pages net.  $5. 00 


SCIENTIFIC  PUBLICATIONS.  13 


ERFURT,  JULIUS.  Dyeing  of  Paper  Pulp ;  a  practi- 
cal treatise  for  the  use  of  paper-makers,  paper-stainers,  students  and 
others.  With  illustrations  and  157  patterns  of  paper  dyed  in  the  pulp, 
with  formulas  for  each.  Translated  into  English  and  edited,  with  ad- 
ditions, by  Julius  Hiibner,  F.  C.  S.  8vo,  cloth,  illustrated,  .net.  $7.50 

Maximum    Stresses   under    Concentrated   Loads. 

Treated  graphically.     Illustrated.     8vo,  cloth $1.50 

EISSLER,  M.    The  Metallurgy  of  Gold;   a  Practical 

Treatise  on  the  Metallurgical  Treatment  of  Gold-Bearing  Ores,  in- 
cluding the  Processes  of  Concentration  and  Chlorination,  and  the 
Assaying,  Melting  and  Refining  of  Gold.  Fifth  Edition,  revised 
and  greatly  enlarged.  Over  300  illustrations  and  numerous  fold- 
ing plates.  8vo,  cloth $7.50 

EISSLER,  M.  The  Hydro-Metallurgy  of  Copper.  Being 

an  account  of  processes  adopted  in  the  Hydro- Metallurgical  treatment 
of  Cupriferous  Ores,  including  the  manufacture  of  Copper  Vitriol.  With 
chapters  on  the  sources  of  supply  of  Copper  and  the  Roasting  of 
Copper  Ores.  With  numerous  diagrams  and  figures.  870,  cloth, 
illustrated net,  $4.50 

The  Metallurgy  of  Silver ;  a  Practical  Treatise  on 

the  Amalgamation,  Roasting  and  Lixivation  of  Silver  Ores,  including 
the  Assaying,  Melting  and  Refining  of  Silver  Bullion.  124  illustra- 
tions. Second  Edition,  enlarged.  8vo,  cloth $4.00 

The  Metallurgy  of  Argentiferous  Lead ;  a  Practical 

Treatise  on  the  Smelting  of  Silver-Lead  Ores  and  the  Refining  of 
Lead  Bullion.  Including  Reports  on  Various  Smelting  Establish- 
ments and  Descriptions  of  Modern  Smelting  Furnaces  and  Plants  in 
Europe  and  America.  With  183  illustrations.  8vo,  cloth $5.00 

Cyanide  Process  for  the  Extraction  of  Gold  and  its 

•  Practical  Application  on  the  Witwatersrand  Gold  Fields  in  South 
Africa.  Third  edition,  revised  and  enlarged.  Illustrations  and  fold- 
ing plates.  8vo,  cloth $3.00 

A  Hand-book  on  Modern  Explosives,  being  a  Prac- 
tical Treatise  on  the  Manufacture  and  use  of  Dynamite,  Gun  Cotton, 
Nitro-Glycerine  and  other  Explosive  Compounds,  including  the  man- 
ufacture of  Collodion-cotton,  with  chapters  on  explosives  in  practical 
application.  Second  Edition,  enlarged  with  150  illustrations. 
12mo,  cloth $5.00 

ELIOT,  C.  W.,  and  STOKER,  F.  H.    A  Compendious 

Manual  of  Qualitative  Chemical  Analysis.  Revised  with  the  co-oper- 
ation of  the  authors,  by  Prof.  William  R.  Nichols.  Illustrated. 
Twentieth  Edition,  newly  revised  by  Prof.  W.  B.  Lindsay. 
12mo,  cloth net  $1.25 

ELLIOT,  Maj.  GEO.  H.  European  Light-House  Sys- 
tems. Being  a  Report  of  a  Tour  of  Inspection  made  in  1873.  51 
engravings  and  21  woodcuts.  8vo,  cloth $5.00 


14  D.  VAN  NOSTBAND  COMPANY'S 


EDDY,  Prof.  H.  T.     Researches  in  Graphical  Statics. 

Embracing  New  Constructions  in  Graphical  Statics,  a  New  General 
Method  in  Graphical  Statics,  and  the  Theory  of  Internal  Stress  in 
Graphical  Statics.  8vo,  cloth $1.50 

EVERETT,  J.  D.    Elementary  Text-Book  of  Physics. 

Illustrated.     Seventh  Edition.     12mo,  cloth $1.50 

EWING,  Prof.  A.  J.     The  Magnetic  Induction  in  Iron 

and  other  metals.  Third  edition,  revised.  159  illustrations.  8vo, 
cloth $4  00 

FAIRIE,  JAMES,  F.  G.  S.    Notes  on  Lead  Ores  ;  their 

Distribution  and  Properties.     12mo,  cloth $1.00 

Notes  on  Pottery  Clays  ;  the  Distribution,  proper- 
ties, Uses  and  Analysis  of  Ball  Clays,  China  Clays  and  China  Stone. 
With  tables  and  formulae.     12mo,  cloth $1.50 

FANNING,  J.  T.      A  Practical  Treatise  on  Hydraulic 

and  Water-Supply  Engineering.  Relating  to  the  Hydrology,  Hydro- 
dynamics, and  Practical  Construction  of  Water- Works  in  North 
America.  180  illustrations.  8vo,  cloth.  fifteenth  Edition,  re- 
vised, enlarged,  and  new  tables  and  illustrations  added.  650 
pages $5.00 

FAY,  I.  W.    The  Coal-tar  Colors;   Origin  and  Chem_ 

istry.     8vo,  cloth,  illustrated In  Press' 

FISH,  J.  C.  L.  Lettering  of  Working  Drawings.  Thir- 
teen plates,  with  descriptive  text.  Oblong,  9x12^,  boards $1.00 

FISHER,   H.   K.   C.   and  DARBY,   W.   C.      Students' 

Guide  to  Submarine  Cable  Testing.  Third  (new  and  enlarged)  edi- 
tion. 8vo,  cloth,  illustrated $3.50 

FISHER,  W.  C.      The  Potentiometer  and  its  Adjuncts. 

8vo,  cloth $2.25 

FISKE,  Lieut.  BRADLEY  A.,  TJ.S.N.     Electricity  in 

Theory  and  Practice ;  or,  The  Elements  of  Electrical  Engineering. 
Eighth  Edition.  8vo,  cloth $2.50 

FLEISCHMANN,  W.  The  Book  of  the  Dairy.  A  Man- 
ual of  the  Science  and  Practice  of  Dairy  Work.  Translated  from  the 
German,  by  C.  M.  Aikman  and  E.  Patrick  Wright.  8vo,  cloth... $4. 00 

FLEMING,  Prof.  J.  A.  The  Alternate  Current  Trans- 
former in  Theory  and  Practice.  Vol.  I — The  Induction  of  Electric 
Currents;  611  pages.  New  edition.  Illustrated.  8vo,  cloth . . .  $5. 00 
Vol.  2,  The  Utilization  of  Induced  Currents.  Illustrated.  8vo, 
cloth $5.00 

Centenary    of  the  Electrical  Current,  1799-1899. 

8vo,  paper,  illustrated 5o 


SCIENTIFIC  PUBLICATIONS.  15. 


FLEMING.  Prof.  J.  A.    Electric  Lamps  and  Electric 

Lighting.  Being  a  course  of  four  lectures  delivered  at  the  Royal  In- 
stitution, April-May,  1894.  8vo,  cloth,  fully  illustrated $3.00 

Electrical  Laboratory  Notes  and  Forms,  Elemen- 
tary and  advanced.     4to,  cloth,  illustrated $5.00 

A  Handbook  for  the  Electrical  Laboratory  and 

Testing  Room.     2  volumes.     8vo,  cloth each  $5.00 

FLETJRY,  HENRY.     The    Calculus    Without  Limits 

or  Infinitesmals.     Translated  by  C.  O.  Mailloux In  Press. 

FOLEY,    NELSON    and    THOS.    PRAY,    Jr.        The 

Mechanical  Engineers'  Reference  Book  for  Machine  and  Boiler  Con- 
struction, in  two  parts.  Part  1 — General  Engineering  Data.  Part  2 
— Boiler  Construction.  With  fifty-one  plates  and  numerous  illustra- 
tions, specially  drawn  for  this  work.  Folio,  half  morocco $25.00 

FORNEY,  MATTHIAS  N.  Catechism  of  the  Locomo- 
tive. Second  Edition,  revised  and  enlarged  Forty-sixth  thousand. 
8vo,  cloth $3.50 

FOSTER,  Gen.  J.  G.,  U.S.A.     Submarine  Blasting  in 

Boston  Harbor,  Massachusetts.  Removal  of  Tower  and  Corwin 
Rocks.  Illustrated  with  7  plates.  4to,  cloth $3.50 

FOSTER,  H.  A.      Electrical  Engineers'  Pocket  Book. 

With  the  Collaboration  of  Eminent  Specialists.  A  handbook  of  use- 
ful data  for  Electricians  and  Electrical  Engineers.  With  innumerable 
tables,  diagrams  and  figures.  Second  edition,  revised.  Pocket  size, 
full  leather,  1000  pages $5.00 

FOSTER,   JAMES.      Treatise  on  the  Evaporation  of 

Saccharine,  Chemical  and  other  Liquids  by  the  Multiple  System  in 
Vacuum  and  Open  Air.  Third  Edition.  Diagrams  and  large 
plates.  8vo,  cloth  $7.50 

FOX,  WM.,  and  C.  W.  THOMAS,  M.  E.    A  Practical 

Course  in  Mechanical  Drawing.  Second  edition,  revised.  12mo, 
cloth  with  plates $1.25 

FRANCIS,  Jas.  B.,  C.E.  Lowell  Hydraulic  Experi- 
ments. Being  a  selection  from  experiments  on  Hydraulic  Motors, 
on  the  Flow  of  Water  over  Weirs,  in  open  Canals  of  uniform  rec- 
tangular section,  and  through  submerged  Orifices  and  diverging 
Tubes.  Made  at  Lowell,  Mass.  Fourth  edition,  revised  and 
enlarged,  with  many  new  experiments,  and  illustrated  with  23 
copper-plate  engravings.  4to,  cloth $15.00 

FULLER,  GEORGE  W.    Report  on  the  Investigations 

into  the  Purification  of  the  Ohio  River  Water  at  Louisville,  Ken- 
tucky, made  to  the  President  and  Directors  of  the  Louisville  Water 
Company.  Published  under  agreement  with  the  Directors.  3  full 
page  plates.  4to,  cloth net,  $10.00 


16  D.  VAN  NOSTRAND  COMPANY'S 


FURNELL,    JOHN.       Students'   Manual    of    Paints, 

Colors,  Oils  and  Varnishes.     8vo,  cloth,  illustrated In  Press. 

GARCKE,  EMILE,  and  J.   M.   FELLS.     Factory  Ac- 

counts  ;  their  principles  and  practice.  A  handbook  for  accountants  and 
manufacturers,  with  appendices  on  the  nomenclature  of  machine  de- 
tails, the  rating  of  factories,  fire  and  boiler  insurance,  the  factory  and 
workshop  acts,  etc.,  including  also  a  large  number  of  specimen  rul- 
ings. Fifth  edition,  revised  and  extended.  8vo,  cloth,  illus...  $3.00 

GEIPEL,  WM.  and  KILGOUR,  M.  H.    A  Pocketbook 

of  Electrical  Engineering  Formulae.     Illustrated.     18mo,  mor.  .$3.00 

GERBER,  NICHOLAS.  Chemical  and  Physical  An- 
alysis of  Milk,  Condensed  Milk  and  Infant's  Milk-Food.  8vo, 
cloth $1.25 

GERHARD,  WM.  P.      Sanitary  Engineering.      12mo, 

cloth  $1.25 

GESCHWIND,  LTJCIEN.     Manufacture  of  Alum  and 

Sulphates,  and  other  Salts  of  Alumnia  and  Iron  ;  their  uses  and  ap- 
plications as  mordants  in  dyeing  and  calico  printing,  and  their  other 
applications  in  the  Arts,  Manufactures,  Sanitary  Engineering,  Agri- 
culture and  Horticulture.  Translated  from  the  French  by  Charles  Sal- 
ter.  With  tables,  figures  and  diagrams.  8vo,  cloth,  illus..  .net.  $5.00 

GIBBS,  WILLIAM  E.  Lighting  by  Acetylene,  Gen- 
erators, Burners  and  Electric  Furnaces.  With  66  illustrations.  /Sec- 
ond edition  revised.  12mo,  cloth $1.50 

GILLMORE,  Gen.  Q.  A.    Treatise  on  Limes,  Hyraulic 

Cements,  and  Mortars.  Papers  on  Practical  Engineering,  United 
States  Engineer  Department,  No.  9,  containing  Reports  of  numerous 
Experiments  conducted  in  New  York  City  during  the  years  1858  to 
1861,  inclusive.  With  numerous  illustrations.  8vo,  cloth $4.00 

Practical  Treatise  on  the  Construction  of  Roads, 

Streets,  and  Pavements.  Tenth  Edition.  With  70  illustrations. 
12mo,  cloth $2.00 

Report  on  Strength  of  the  Building  Stones  in  the 

United  States,  etc.    8vo,  illustrated,  cloth $1.00 

GOLDING,    HENRY    A.      The    Theta-Phi    Diagram. 

Practically  applied  to  Steam,  Gas,  Oil  and  Air  Engines.  12mo,  cloth. 
Illustrated net,  $1.25 

GOODEVE,  T.  M.     A  Text-Book  on  the  Steam-Engine. 

With  a  Supplement  on  Gas-Engines.  Twelfth  Edition,  enlarged. 
143  illustrations.  12mo,  cloth '. $2.00 

GORE,  G.,  F.  R.  S.  The  Art  of  Electrolytic  Separa- 
tion of  Metals,  etc.  (Theoretical  and  Practical.)  Illustrated.  8vo, 
cloth..  $3.50 


SCIENTIFIC  PUBLICATIONS.  17 


GOULD,  E.  SHERMAN.    The  Arithmetic  of  the  Steam 

Engine.     8vo,  cloth $1.00 

-  Practical  Hydrostatics  and  Hydrostatic  Formu- 
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GRAY,  JOHN  B.Sc.      Electrical  Influence  Machines; 

their  Historical  Developement,  and  Modern  Forms,  with  instructions 
for  making  them.  With  numerous  figures  and  diagrams.  Second 
edition,  revised  and  enlarged.  12mo,  cloth,  illustrated,  296  pp.. $2. 00 

GRIFFITHS,  A.   B.,   Ph.D.    A  Treatise  on  Manures, 

or  the  Philosophy  of  Manuring.  A  Practical  Hand-Book  for  the 
Agriculturist,  Manufacturer,  and  Student.  12mo,  cloth $3.00 

Dental  Metallurgy ;  A  Manual  for  Students  and 

Dentists.     8vo,  cloth,  illustrated,  208  pages net,  $3.50 

GROSS,  EMANUEL.  Hops,  in  their  Botanical,  Agri- 
cultural and  Technical  Aspect,  and  as  an  article  of  Commerce.  Trans- 
lated from  the  German  by  Charles  Salter.  With  tables,  diagrams  and 
illustrations.  8vo,  cloth,  illustrated net.  $4.50 

GROVER,  FREDERICK.  Practical  Treatise  on  Mod- 
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GRUNER,  ANTON.      Power-loom  Weaving  and  Yarn 

Numbering,  according  to  various  systems,  with  conversion  tables.  An 
auxiliary  and  text-book  for  pupils  of  weaving  schools,  as  well  as  for 
self -instruction,  and  for  general  use  by  those  engaged  in  the  weaving 
industry.  Illustrated  with  colored  diagrams.  8vo,  cloth. .  .net.  $3.00 

GURDEN,    RICHARD    LLOYD.      Traverse    Tables: 

computed  to  4  places  Decimals  for  every  °  of  angle  up  to  100  of  Dis- 
tance. For  the  use  of  Surveyors  and  Engineers.  New  Edition. 
Folio,  half  morocco $7.50 

GUY,  ARTHUR  F.     Electric  Light  and  Power,  giving 

the  Eesult  of  Practical  Experience  in  Central-Station  Work.  8vo, 
cloth.  Illustrated $2.50 

GUY,  A.  E.     Experiments  on  the  Flexure  of  Beams, 

resulting  in  the  Discovery  of  New  Laws  of  Failure  by  Buckling. 
Reprinted  from  the  "American  Machinist."  With  diagrams  and 

folding  plates.     8vo,  cloth,  illustrated,  122  pages net.  $1.25 

Postage,      .10 

HAEDER,  HERMAN,  C.  E.    A  Handbook  on  the  Steam 

Engine.  With  especial  reference  to  small  and  medium  sized  engines. 
For  the  use  of  Engine  Makers,  Mechanical  Draughtsmen,  Engineer- 
ing Students  and  Users  of  Steam  Power.  Translated  from  the  Ger- 
man, with  considerable  additions  and  alterations,  by  H.  H.  P.  Powles. 
Third  English  edition,  revised.  8vo,  cloth,  illus.,  458  pages. .  .$3.00 


18  D.  VAN  NOSTKAND  COMPANY'S 


HALL,  WM.  S.   Prof.      Elements  of  the  Differential 

and  Integral  Calculus.  Fourth  edition,  revised.  8vo,  cloth.  Illus- 
trated   net,  $2.25 

Descriptive  Geometry,  with  numerous  Problems 

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of  text  and  a  4to  atlas  of  31  plates.     2  vols.,  cl net.  $3.50 

Postage.       .32 

HALSEY,  F.   A.    Slide  Valve  Gears,  an  Explanation 

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HAMILTON",  W.  G.    Useful  Information  for  Railway 

Men.  Tenth  Edition,  revised  and  enlarged.  562  pages,  pocket 
form.  Morocco,  gilt $2.00 

HAMMER,  W.   J.      Radium,  and  other  Radio-active 

Substances  ;  Polonium,  Actinium  and  Thorium.  With  a  considera- 
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Ultra- Violet  Light.  With  diagrams,  engravings  and  Photographic 
plates.  8vo,  cloth,  illustrated,  72  pp $1.00 

HANCOCK,  HERBERT.    Text-Book  of  Mechanics  and 

Hydrostatics,  with  over  500  diagrams.      8vo,  cloth $1.75 

HAR,RISON,    W.    B.      The    Mechanics'    Tool    Book. 

With  Practical  Rules  and  Suggestions  for  use  of  Machinists,  Iron- 
Workers,  and  others.  Illustrated  with  44  engravings.  12mo, 
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HART,    JOHN   W.       External   Plumbing   Work;    a 

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Principles  of  Hot  Water  Supply.    With  numerous 

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SCIENTIFIC  PUBLICATIONS.  19 


HASKINS,    C.   H.      The  Galvanometer  and  its   Uses. 

A  Manual  for  Electricians  and  Students.  Fourth  edition.  12mo, 
cloth $1.50 

H  ATJFF,  W.  A.   American  Multiplier ;  Multiplications 

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also  tables  of  circumferences  and  areas  of  circles.      Cloth,  6£  x  15J. 

$5. 00 

HATJSBRAND,    E.      Drying   by    Means  of  Air  and 

Steam.  With  explanations,  formulas  and  tables,  for  use  in  practice. 
Translated  from  the  German  by  A.  C.  Wright,  M.  A.  12mo,  cloth, 
illustrated $2.00 

—  Evaporating,  Condensing  and  Cooling  Apparatus  ; 

Explanations,  Formulae,  and  Tables  fpr  Use  in  Practice.  Translated 
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With  numerous  figures,  tables  and  diagrams.  8vo,  cloth,  illustrated, 
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HATJSNER,  A.    Manufacture  of  Preserved  Foods  and 

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German  Edition,  by  Arthur  Morris  and  Herbert  Robson,  B.  Sc.  8vo, 
cloth,  illustrated,  223  pages net,  $3.00 

HAWKE,  WILLIAM  H.  The  Premier  Cipher  Tele- 
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-  100,000  Words  Supplement  to  the  Premier  Code. 

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HAWKINS,  C.  C.,  and  WALLIS,  F.      The  Dynamo; 

its  Theory,  Design  and  Manufacture.  190  illustrations,  12mo,  cloth, 
$3. 00 

HAY,    ALFRED.      Principles   of  Alternate  -  Current 

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HEAP,  Major  D.  P.,  TJ.  S.  A.   Electrical  Appliances  of 

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250  illustrations.  8vo,  cloth $2.00 

HEAVISIDE,    OLIVER.        Electromagnetic    Theory. 

8vo,  cloth,  two  volumes each,  $5.00 

HEERMANN,  PAUL.  Dyers'  Materials :  an  intro- 
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HENRICI,  OLAUS.     Skeleton  Structures,   Applied  to 

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HERRMANN,    Gustav.      The    Graphical    Statics    of 

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plates.  Fourth  Edition $2.00 

HERMANN,  FELIX.  Painting  on  Glass  and  Porce- 
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HERZFELD,  DR.  J.    The  Technical  Testing  of  Yarns 

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HE  WSON,  WM.   Principles  and  Practice  of  Embanking 

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HILL,  JOHN  W.      The  Purification  of  Public  Water 

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Interpretation  of  Water  Analysis.     12mo,  cloth. 

In  Press. 

HOBBS,  W.  R.  P.  The  Arithmetic  of  Electrical  Meas- 
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HOFF,  WM.  B.,  Com.  U.  S.  Navy.    The  Avoidance  of 

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HOLLE  Y,  ALEXANDER  L.  Railway  Practice.  Ameri- 
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Steam,  including  the  Materials  and  Construction  of  Coal-burning 
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ings, Street  Railways,  etc.  With  77  lithographed  plates.  Folio, 
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HOLMES,  A.  BROMLEY.  The  Electric  Light  Popu- 
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HOPKINS,  NE VIL  M.      Model   Engines    and    Small 

Boats.  New  Methods  of  Engine  and  Boiler  Making  with  a  chapter  on 
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HOSPITALIER,  E.    Polyphased  Alternating  Currents. 

Illustrated.     8vo,  cloth $1.40 


SCIENTIFIC  PUBLICATIONS.  21 


HOWARD,  C.  R.  Earthwork  Mensuration  on  the  Basis 

of  the  Prismoidal  Formulae.  Containing  Simple  and  Labor-saving 
Method  of  obtaining  Prismoidal  Contents  directly  from  End  Areas. 
Illustrated  by  Examples  and  accompanied  by  Plain  Eules  for  Practi- 
cal Uses.  Illustrated.  8vo,  cloth $1.50 

HO  WORTH,  J.    Art  of  Repairing  and  Riveting  Glass, 

China  and  Earthenware.  Second  edition.  8vo,  pamphlet,  illus- 
trated  net,  $0.50 

HTJBBARD,  ERNST.  The  Utilization  of  Wood- 
Waste  :  a  Complete  Account  of  the  Most  Advantageous  Methods  of 
Working  Up  Wood  Befuse,  especially  Sawdust,  Exhausted  Dye 
Woods  and  Tan  as  Fuel,  as  a  Source  of  Chemical  Products  for  Arti- 
ficial Wood  Compositions,  Explosives,  Manures,  and  many  other  Tech- 
nical Purposes.  Translated  'from  the  German  of  the  Second  revised 
and  enlarged  edition.  8vo,  cloth,  illustrated,  192  pages. .  .net.  $2.50 

HUMBER,  WILLIAM,  C.  E.    A  Handy  Book  for  the 

Calculation  of  Strains  in  Girders,  and  Similar  Structures,  and  their 
Strength ;  Consisting  of  Formulae  and  Corresponding  Diagrams,  with 
numerous  details  for  practical  application,  etc.  Fourth  Edition. 
12mo,  cloth $2.50 

HURST,    GEO.  H.,  F.  C.  S.      Color;    a    Hand-book    of 

the  Theory  of  Color.  A  practical  work  for  the  Artist,  Art  Student, 
Painter,  Dyer  and  Calico  Printer  and  Others.  Illustrated  with  10 
colored  plates  and  72  illustrations.  8vo,  cloth net,  $2.50 

Dictionary  of  Chemicals  and  Raw  Products  used 

in  the  Manufacture  of  Paints,  Colors,  Varnishes  and  Allied  Prepara- 
tions. 8vo,  cloth net,  $3.00 

Lubricating  Oils,  Fats  and  Greases ;  Their  Origin, 

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Soaps;  A  Practical  Manual  of  the  Manufacture  of 

Domestic,  Toilet  and  other  Soaps.  Illustrated  with  66  Engravings. 
8vo,  cloth net,  $5.00 

HUTCHINSON,  W.  B.  Member  of  the  New  York  Bar. 
Patents  and  How  to  Make  Money  out  of  Them.  12mo,  cloth.  ..$1.25 

HUTTON,  W.  S.  Steam  Boiler  Construction.  A  Prac- 
tical Hand  Book  for  Engineers,  Boiler  Makers  and  Steam  Users. 
Containing  a  large  collection  of  rules  and  data  relating  to  recent 
practice  in  the  design,  construction,  and  working  of  all  kinds  of 
stationary,  locomotive  and  marine  steam-boilers.  With  upwards  of 
540  illustrations.  Fourth  Edition,  carefully  revised  and  much  en- 
larged. 8vo,  cloth $6.00 

Practical    Engineer's    Hand-Book,    Comprising   a 

treatise  on  Modern  Engines  and  Boilers,  Marine,  Locomotive  and 
Stationary.  Fourth  Edition.  Carefully  revised  with  additions. 
With  upwards  of  570  illustrations.  8vo,  cloth $7.00 


22  D.  VAN  NOSTBAND  COMPANY'S 


HART,  JOHN  W.    The  Works'  Manager's  Hand-Book 

of  Modern  Rules,  Tables,  and  Data  for  Civil  and  Mechanical  Engineers. 
Millwrights  and  Boiler-makers,  etc. ,  etc.  With  upwards  of  150  illus- 
trations. Fifth  Edition.  Carefully  revised,  with  additions.  8vo, 
cloth $6.00 

INGLE,  HERBERT.  Manual  of  Agricultural  Chem- 
istry. 8vo,  cloth,  illustrated,  388  pages net.  $3.00 

INNES,  CHARLES  H.    Problems  in  Machine  Design, 

For  the  Use  of  Students,  Draughtsmen  and  others.  Second  edition. 
12mo,  cloth net,  $2.00 

Centrifugal  Pumps,  Turbines,  and  Water  Motors. 

Including  the  Theory  and  Practice  of  Hydraulics.  Third  and  en- 
larged edition.  12mo,  cloth net,  $2. 00 

ISHERWOOD,  B.  F.  Engineering  Precedents  for  Steam 

Machinery.  Arranged  in  the  most  practical  and  useful  manner  for 
Engineers.  With  illustrations.  2vols.ini.  8vo,  cloth $2.50 

JAMIESON,  ANDREW,  C.E.    A  Text-Book  on  Steam 

and  Steam-Engines.  Specially  arranged  for  the  use  of  Science  and 
Art,  City  and  Guilds  of  London  Institute,  and  other  Engineering 
Students.  Thirteenth  Edition.  Illustrated.  12mo,  cloth $3.00 

Elementary  Manual  on  Steam  and  the  Steam  En- 
gine. Specially  arranged  for  the  use  of  First- Year  Science  and  Art, 
City  and  Guilds  of  London  Institute,  and  other  Elementary  Engineer- 
ing Students.  Third  Edition.  12mo,  cloth . .  .$1.50 

JANNETTAZ,  EDWARD.  A  Guide  to  the  Determina- 
tion of  Rocks  :  being  an  Introduction  to  Lithology.  Translated  from 
the  French  by  G.  W.  Plympton,  Professor  of  Physical  Science  at 
Brooklyn  Polytechnic  Institute.  12mo,  cloth $1.50 

JEHL,  FRANCIS.  Member  A.  I.  E.  E.  The  manu- 
facture of  Carbons  for  Electric  Lighting  and  Other  Purposes.  A 
Practical  Hand-book,  giving  a  complete  description  of  the  art  of  mak- 
ing carbons,  electros,  etc.  The  various  gas  generators  and  furnaces 
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numerous  diagrams,  tables  and  folding  plates.  8 vo,  cloth,  illus'd .  $4. 00 

JENNISON,  FRANCIS  H.    The  Manufacture  of  Lake 

Pigments  from  Artificial  Colors.  A  useful  handbook  for  color  manu- 
facturers, dyers,  color  chemists,  paint  manufacturers,  drysalters, 
wall-paper  makers,  enamel  and  surface-paper  makers.  With  fifteen 
plates  illustrating  the  various  methods  and  errors  that  arise  in  the 
different  processes  of  production.  8vo,  cloth,  illustrated  .  .net,  $3.00 

JOHNSON,  W.  McA.  "  The  Metallurgy  of  Nickel." 
.In  Press. 

JOHNSTON,  Prof.  J.  F.  W.,  and  CAMERON,  Sir  Chas. 

Elements  of  Agricultural  Chemistry  and  Geology.  Seventeenth  Edi- 
tion. 12mo,  cloth $2.60 


SCIENTIFIC  PUBLICATIONS.  23 


JONES,  HARRY  C.      Outlines  .  of   Electrochemistry. 

With  tables  and  diagrams.     4to,  cloth,  illustrated $1.50 

JONES,  M.  W.     The  Testing  and  Valuation  of  Raw 

Materials  used  in  Paint  and  Color  Manufacture.    12mo,  cl...net.  $2.00 

JOYNSON,  F.  H.      The  Metals  used  in  Construction. 

Iron,  Steel,  Bessemer  Metal,  etc.     Illustrated.     12mo,  cloth 75 

Designing  and  Construction  of  Machine  Gearing. 

Illustrated.     8vo,  cloth $2.00 

JUPTNER,  HANNS  P.  V.    Siderology.    The  Science  of 

of  Iron.  (The  Constitution  of  Iron  Alloys  and  Iron.)  Translated 
from  the  German.  8vo,  cloth,  345  pages,  illustrated net.  $5.00 

KANSAS  CITY  BRIDGE,  THE     With  an  Account  of 

the  Regimen  of  the  Missouri  River  and  a  Description  of  the  Methods 
used  for  Founding  in  that  River.  By  O.  Chanute,  Chief  Engineer,  and 
George  Morrison,  Assistant  Engineer.  Illustrated  with  5  lithographic 
views  and  12  plates  of  plans.  4to,  cloth $6.00 

KAPP,  GISBERT,  C.E.  Electric  Transmission  of  Ener- 
gy and  its  Transformation,  Subdivision,  and  Distribution.  A  Practical 
hand-book.  Fourth  JZdition,  revised  12mo,  cloth $3.50 

Dynamos,  Motors,  Alternators  and  Rotary  Con- 
verters. Translated  from  the  Third  German  Edition,  by  Harold  H. 
Simmons,  A.  M.  I.  E.  E. ,  with  numerous  diagrams  and  figures.  8vo, 
cloth,  507  pages $4.00 

KEIM,    ADOL.PH    W.      Prevention   of  Dampness  in 

Buildings  ;  with  Remarks  on  the  Causes,  Nature  and  Effects  of  Saline 
Efflorescences  and  Dry  Rot.  For  Architects,  Builders,  Overseers, 
Plasterers,  Painters  and  House  Owners.  Translated  from  the  Second 
revised,  German  edition.  With  colored  plates  and  diagrams.  8vo, 
cloth,  illustrated,  115  pages net.  $2.00 

KELiSEY,  W.  R.      Continuous  Current  Dynamos  and 

Motors,  and  Their  Control ;  being  a  series  of  articles  re-printed  from 
The  Practical  Engineer,  and  completed  by  W.  R.  Kelsey.  With 
many  figures  and  diagrams.  8vo,  cloth,  illustrated.  440  pages,  $2.51) 

KEMP,  JAMES  FURMAN,  A.  B.,  E.  M.  A  Hand- 
Book  of  Rocks  ;  for  use  without  the  microscope.  With  a  glossary 
of  the  names  of  rocks  and  of  other  lithological  terms.  8vo,  cloth,  il- 
lustrated   .  .$1.50 

KEMPE,  H.   R.      The    Electrical    Engineer's    Pocket 

Book  of  Modern  Rules,  Formulae,  Tables  and  Data.  Illustrated. 
32mo.  Morocco,  gilt $1.75 

KENNELLY,  A.  E.  Theoretical  Elements  of  Electro- 
Dynamic  Machinery.  8vo,  cloth $1.50 


24  D.  VAN  NOSTRAND  COMPANY'S 


KILGOUR,  M.  H.,  SWAN,  H.,  and  BIGGS,  C.  H.  W. 

Electrical  Distribution  ;  Its  Theory  and  Practice.  174  Illustrations. 
12mo,  cloth $4.00 

KING,  W.  H.    Lessons  and  Practical  Notes  on  Steam. 

The  Steam-Engine,  Propellers,  etc.,  for  Young  Marine  Engineers, 
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States  Navy.  Nineteenth  Edition,  enlarged.  8vo,  cloth $2.00 

KINGDON,  J.  A.  Applied  Magnetism.  An  introduc- 
tion to  the  Design  of  Electromagnetic  Apparatus.  8vo,  cloth.  ..$3.00 

KIRKALDY,   Wm.   G.    Illustrations  of  David  Kirk- 

aldy's  System  of  Mechanical  Testing,  as  Originated  and  Carried  On 
by  him  during  a  Quarter  of  a  Century.  Comprising  a  Large  Selection 
of  Tabulated  Results,  showing  the  Strength  and  other  Properties  of 
Materials  used  in  Construction,  with  Explanatory  Text  and  Historical 
Sketch.  Numerous  engravings  and  25  lithographed  plates.  4to, 
cloth $20.00 

KIRKBRIDE,  J.  Engraving  for  Illustration ;  Histor- 
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KIRKWOOD,   JAS.   P.     Report    on   the    Filtration   of 

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KLEIN,  J.  F.    Design  of  a  High  Speed  Steam  Engine. 

With  Notes,  Diagrams,  Formulas,  and  Tables.  Second  Edition  Re- 
vised and  Enlarged.  8vo,  cloth,  illustrated,  257  pages. . . .  .net,  $5.00 

KNIGHT,  AUSTIN  M.,  (Lieutenant- Commander  U.  S.  N.) 
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Half  morocco $7.50 

KOliLER,    THEODOR.       The    Utilization    of   Waste 

Products.  A  Treatise  on  the  Rational  Utilization,  Recovery  and 
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man Second  Revised  Edition.  With  numerous  diagrams.  8vo,  cloth, 
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Cosmetics :  A  Handbook  of  the  Manufacture,  Em- 
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ties. Translated  from  the  German  by  Chas.  Salter.  8vo,cloth,  net,  $2.50 

KRAUCH,  Dr.  C.      Testing  of  Chemical  Reagents  for 

Purity.  Authorized  translation  of  the  Third  edition,  by  J.  A.  Wil- 
liamson and  L.  W.  Dupre.  With  additions  and  emendations  by  the 
author.  8vo,  cloth net.  $4.50 

LAMBERT,   THOMAS.      Lead,   and  Its   Compounds. 

With  tables,  diagrams  and  folding  plates.  8vo,  cloth,  illustrated, 
228  pages net.  $3.50 


SCIENTIFIC  PUBLICATIONS.  25 


LAMBERT,  THOMAS  Bone  Products  and  Manures: 

an  account  of  the  most  recent  improvements  in  the  manufacture  of 
Fat,  Glue,  Animal  Charcoal,  Size,  Gelatine  and  Manures.  With  plans 
and  diagrams.  8vo,  cloth,  Illustrated net  $3.00 

LAMPRECHT,  ROBERT.    Recovery  Work  after  Pit 

Fires ;  a  description  of  the  principal  methods  puisued,  especially  in 
fiery  mines,  and  of  the  various  appliances  employed,  such  as  respira- 
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grams. Translated  from  the  German  by  Charles  Salter.  8vo,  cloth, 
illustrated net,  $4.00 

LARRABEE,  C.  S.  Cipher  and  Secret  Letter  and  Tele- 
graphic Code,  with  Hog's  Improvements.  The  most  perfect  Secret 
Code  ever  invented  or  discovered.  Impossible  to  read  without  the 
key.  18mo,  cloth 60 

LASSAR-COHN,  Dr.  An  Introduction  to  Modern  Sci- 
entific Chemistry,  in  the  form  of  popular  lectures  suited  to  Universi- 
ty Extension  Students  and  general  readers.  Translated  from  the  au- 
thor's corrected  proofs  for  the  second  German  edition.  By  M.  M. 
Pattison  Muir,  M.  A.  12mo,  cloth,  illustrated $2.00 

LEASK,  A.  RITCHIE.      Breakdowns  at  Sea  and  How 

to  Eepair  Them.  With  eigthy-nine  illustrations.  Second  Edition. 
8vo,  cloth $2.00 

Triple  and   Quadruple    Expansion   Engines    and 

Boilers  and  their  Management.  With  fifty-nine  illustrations.  Third 
edition^  revised.  12mo,  cloth $2.00 

Refrigerating  Machinery :  Its  Principles  and  Man- 
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LECKY,  S.  T.  S.    "  Wrinkles  "  in  Practical  Navigation. 

With  130  illustrations.     8vo,  cloth     Ninth  Edition,  revised $8.40 

LEFEVRE,    LEON.      Architectural   Pottery:  Bricks, 

Tiles,  Pipes,  Enameled  Terra-Cottas,  Ordinary  and  Incrusted  Quar- 
ries, Stoneware  Mosaics,  Faiences,  and  Architectural  Stoneware. 
With  tables,  plates  and  950  cuts  and  illustrations.  With  a  preface  by 
M.  J.-C.  Formigd.  Translated  from  the  French  by  K.  H.  Bird,  M.  A. 
and  W.  Moore  Binns.  4to,  cloth,  illustrated net  $7.50 

LEHNER,  SIGMTJND.     Ink  Manufacture :    including 

Writing,  Copying,  Lithographic,  Marking,  Stamping  and  Laundry 
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and  Herbert  Eobson,  B.  Sc.  8vo,  cloth,  illustrated,  162  pages. 
net,  $2.50 

LEMSTROM,  Dr.  Electricity  in  Horticulture.  Illus- 
trated   .  .In  Press. 


26  D.  VAN  NOSTRAND  COMPANY'S 

LEVY,   C.   L.    Electric  Light  Primer.    A  Simple  and 

Comprehensive  digest  of  all  the  most  important  facts  connected  with 
the  running  of  the  dynamo,  and  electric  lights,  with  precautions  for 
safety.  For  the  use  of  persons  whose  duty  it  is  to  look  after  the 
plant.  8vo,  paper $  .50 

LIVACHE,  AGH..—(Ingenieur  Civil  De*  Mines.)  The  Man- 
ufacture of  Varnishes,  Oil  Crushing,  Refining  and  Boiling  and  Kind- 
red Industries.  Describing  the  Manufacture  and  Chemical  and  Phy- 
sical Properties  of  Spirit  Varnishes  and  Oil  Varnishes  ;  Haw  Mater- 
ials ;  Resins  ;  Solvents  and  Coloring  Principles  ;  Drying  Oils  ;  their 
Extraction,  Properties  and  Applications,  Oil  Refining  and  Boiling  ; 
The  Manufacture,  Employment  and  Testing  of  Various  Varnishes 
Translated  from  the  French,  by  John  Geddes  Mclntosh.  Greatly 
extended  and  adapted  to  English  practice.  With  numerous 
original  recipes,  by  the  translator.  Illustrated  with  cuts  and  dia- 
grams. 8vo,  cloth,  illustrated net.  $5.00 

LIVERMORE,  V.  P.     &  JAMES  WILLIAMS.     How 

to  Become  a  Competent  Motorman.  Being  a  Practical  Treatise  on  the 
Proper  Method  of  Operating  a  Street  Railway  Motor  Car  :  also  giving 
details  how  to  overcome  certain  defects.  16mo,  cloth,  illustrates,  132 
pages .$1.00 

LOBBEN,  PEDER,  M.  E.    Machinists'  and  Draftsmen's* 

Hand-Book,  containing  Tables,  Rules  and  Formulas,  with  numerous 
examples,  explaining  the  principles  of  mathematics  and  mechanics,  as 
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all  interested  in  Mechanical  work.  Illustrated  with  many  cuts  and 
diagrams.  8vo,  cloth $2.50 

LOCKE,  ALFRED  G.  and  CHARLES  G.     A  Practical 

Treatise  on  the  Manufacture  of  Sulphuric  Acid.  With  77  Construe, 
tive  Plates  drawn  to  Scale  Measurements,  and  other  Illustrations- 
Royal  8vo,  cloth $10.00 

LOCKERT,    LOUIS.      Petroleum    Motor-Cars.    12mo, 

cloth $1.50 

LOCKWOOD,  THOS.  D.     Electricity,  Magnetism,  and 

Electro-Telegraphy.  A  Practical  Guide  for  Students,  Operators,  and 
Inspectors.  8vo,  cloth.  Third  Edition $2.50 

Electrical  Measurement  and  the  Galvanometer ;  Its 

Construction  and  Uses.  Second  Edition.  32  illustrations.  12mo, 
cloth $1.50 

LODGE,  OLIVER  J.  Elementary  Mechanics,  includ- 
ing Hydrostatics  and  Pneumatics.  Revised  Edition.  12mo, 
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Signalling  Across  Space,  Without  Wires ;  Being 

a  description  of  the  work  of  Hertz  and  his  successors.  With  numerous 
diagrams  and  half  tone  cuts,  and  additional  remarks  concerning  the 
application  to  Telegraphy  and  later  developments.  Third  edition. 
8vo,  cloth,  illustrated net,  $2.00 


SCIENTIFIC  PUBLICATIONS.  27 


LORD,  R.  T.  Decorative  and  Fancy  Fabrics.  A  val- 
uable Book  with  designs  and  illustrations  for  manufacturers  and  de- 
signers of  Carpets,  Damask,  Dress  and  all  Textile  Fabrics.  8vo, 
cloth,  illustrated net,  $3.50 

LORING,  A.  E.    A  Hand-Book  of  the  Electro-Magnetic 

Telegraph.    Cloth,  boards.     New  and  enlarged  edition 50 

LUCE,   Com.    S.   B.      Text-Book  of  Seamanship.    The 

Equipping  and  Handling  of  Vessels  under  Sail  or  Steam.  For  the 
use  of  the  U.  S.  Naval  Academy.  Revised  and  enlarged  edition, 
by  Lt.  Wm.  S.  Benson .  8vo,  cloth $10.00 

LUNGE,    GEORGE.    Ph.  D.     Coal-Tar  and  Ammonia; 

being  the  third  and  enlarged  edition  of  "A  Treatise  on  the  Distilla- 
tion of  Coal-tar  and  Ammoniacal  Liquor,"  with  numerous  tables,  fig- 
ures and  diagrams.  Thick  8vo,  cloth,  illustrated net  $15.00 

A  Theoretical  and  Practical  Treatise  on  the  Man- 
ufacture of  Sulphuric  Acid  and  Alkali  with  the  Collateral  Branches. 
Vol.  I.  Sulphuric  Acid.  Second  Edition,  Revised  and  enlarged. 

342  illustrations.     8vo,  cloth $15.00 

Vol.  II.  Second  Edition,  revised  and  enlarged.  8vo,  cloth.  .$16.80 
Vol.  III.  8vo,  cloth.  New  Edition,  1896 $15.00 

LUNGE,  GEO.,  and  HURTER,  F.    The  Alkali  Maker's 

Hand  Book.  Tables  and  Analytical  Methods  for  Manufacturers  of 
Sulphuric  Acid,  Nitric  Acid,  Soda,  Potash  and  Ammonia.  Second 
Edition.  12mo,  cloth $3.00 

LUPTON,    A.,    G.    D.    A.    PARR    and   H.    PERKIN. 

Electricity  as  Applied  to  Mining.  With  tables,  diagrams  and  folding 
plates.  8vo,  cloth,  illustrated,  280  pages net.  $3.50 

LUQUER,  LEA  McILVAINE,   Ph.   D.      Minerals  in 

Rock  Sections.  The  Practical  Method  of  Identifying  Minerals  in 
Rock  Sections  with  the  Microscope.  Especially  arranged  for 
Students  in  Technical  and  Sientific  Schools.  8vo,  cloth.  Illus- 
trated  net,  $1.50 

MACCORD,  Prof.  C.  W.    A  Practical  Treatise  on  the 

Slide- Valve  by  Eccentrics,  examining  by  methods  the  action  of  the 
Eccentric  upon  the  Slide- Valve,  and  explaining  the  practical  processes 
of  laying  out  the  movements,  adapting  the  Valve  for  its  various 
duties  in  the  Steam-Engine.  Second  Edition.  Illustrated.  4to, 
cloth $2.50 

MACKROW,  CLEMENT.    The  Naval  Architect's  and 

Ship-Builder's  Pocket-Book  of  Formulae,  Rules  and  Tables ;  and 
Engineers'  and  Surveyors'  Handy-Book  of  Reference.  Eighth  edi- 
tion, revised  and  enlarged.  16mo,  limp  leather,  illustrated.. .  .$5.00 

MAGUIRE,  Capt.   EDWARD,  U.  S.  A.      The  Attack 

and  Defence  of  Coast  Fortifications.  With  Maps  and  Numerous 
Illustrations.  8vo,  cloth $2.50 


28  D.  VAN  NOSTEAND  COMPANY'S 


MAGUIRE,  WM.   R.        Domestic  Sanitary  Drainage 

and  Plumbing  Lectures  on  Practical  Sanitation.  332  illustrations. 
8vo  $4.00 

MARKS,  EDWARD  C.  R.      Mechanical    Engineering 

Materials  :  Their  Properties  and  Treatment  in  Construction.  12mo, 
cloth.  Illustrated 60 

—  Notes  on  the  Construction  of  Cranes  and  Lifting 

Machinery.  With  numerous  diagrams  and  figures.  New  and  en- 
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— -  Notes  on  the  Construction  and  Working  of  Pumps. 

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MARKS,   G.   C.      Hydraulic  Power    Engineering :    a 

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by  Hydraulic  Machinery.  With  over  two  hundred  diagrams  and 
tables.  8vo,  cloth,  illustrated $3.50 

MAVER,  WM.    American  Telegraphy :     Systems,  Ap- 
paratus, Operation.     450  illustrations.     8vo,  cloth $5.00 

MAYER,   Prof.   A.   M.      Lecture   Notes    on  Physics. 

8vo,  cloth $2.00 

McCTJLLOCH,    Prof.    R.   S.      Elementary  Treatise  on 

the  Mechanical  Theory  of  Heat,  and  its  application  to  Air  and  Steam 
Engines.  8vo,  cloth ' $3.50 

McNEILL,   BEDFORD.      McNeill's  Code.      Arranged 

to  meet  the  requirements  of  Mining,  Metallurgical  and  Civil  Engi- 
neers, Directors  of  Mining,  Smelting  and  other  Companies,  Bankers, 
Stock  and  Share  Brokers,  Solicitors,  Accountants,  Financiers,  and 
General  Merchants.  Safety  and  Secrecy.  8vo,  cloth  $6.00 

McPHERSON,   J.  A.    (A.  M  Inst.  C,  M)      Waterworks 

Distribution  ;  a  practical  guide  to  the  laying  out  of  systems  of  distrib- 
uting mains  for  the  supply  of  water  to  cities  and  towns.  With  tables, 
folding  plates  and  numerous  full-page  diagrams.  8vo,  cloth,  ill.  $2.50 

MERRITT,    WM.    HAMILTON.      Field    Testing    for 

Gold  and  Silver.  A  Practical  Manual  for  Prospectors  and  Miners. 
With  numerous  half-tone  cuts,  figures  and  tables.  16mo,  limp 
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METAL  TURNING.    By  a  Foreman  Pattern  Maker. 

Illustrated  with  81  engravings.     12mo,  cloth $1.50 

MICHELL,  STEPHEN.  Mine  Drainage ;  being  a  com- 
plete Practical  Treatise  on  Direct-Acting  Underground  Steam  Pump- 
ing Machinery.  Containing  many  folding  plates,  diagrams  and  tables. 
Second  edition,  re-written  and  enlarged.  Thick,  8vo,  cloth,  illus. 

$10.00 


SCIENTIFIC  PUBLICATIONS.  29 


MINIFIE,  WM.  Mechanical  Drawing.    A  Textbook  of 

Geometrical  Drawing  for  the  use  of  Mechanics  and  Schools,  in  which 
the  Definitions  and  Rules  of  Geometry  are  familiarly  explained ;  the 
Practical  Problems  are  arranged  from  the  most  simple  to  the  more 
complex,  and  in  their  description  technicalities  are  avoided  as  much  as 
possible.  With  illustrations  for  Drawing  Plans,  Sections,  and  Eleva- 
tions of  Railways  and  Machinery ;  an  Introduction  to  Isometrical  Draw- 
ing, and  an  Essay  on  Linear  Perspective  and  Shadows,  Illustrated  with 
over  200  diagrams  engraved  on  steel.  Ninth  thousand.  With  an 
appendix  on  the  Theory  and  Application  of  Colors.  8vo,  cloth.  .$4.00 

Geometrical  Drawing.   Abridged  from  the  Octavo 

edition,  for  the  use  of  schools.  Illustrated  with  48  steel  plates. 
Ninth  edition.  12mo,  cloth $2.00 

MODERN  METEOROLOGY.   A  Series  of  Six  Lectures, 

delivered  under  the  auspices  of  the  Meteorological  Society  in  1870. 
Illustrated.  12mo,  cloth $1.50 

MOORE,  E.  C.  S.  New  Tables  for  the  Complete  Solu- 
tion of  Ganguillet  and  Kutter's  Formula  for  the  flow  of  liquids  in 
open  channels,  pipes,  sewers  and  conduits.  In  two  parts.  Part  I, 
arranged  for  1,080  inclinations  from  1  over  1,  to  1  over  21,120  for 
fifteen  different  values  of  (ri).  Part  II,  for  use  with  all  other  values 
of  (n).  With  large  folding  diagram.  8vo,  cloth,  illustrated,  .net,  $5.00 

MOREING,  C.  A.,  and  NEAL,  THOMAS.    New  Gen- 

eral  and  Mining  Telegraph  Code.  676  pages  alphabetically  arranged. 
For  the  use  of  mining  companies,  mining  engineers,  stockbrokers, 
financial  agents,  and  trust  and  finance  companies.  8th  edition.  8vo, 
cloth $5.00 

MOSES,  ALFRED  J.,  and  PARSONS,  C.  L.    Elements 

of  Mineralogy,  Crystallography  and  Blowpipe  Analysis  from  a  prac- 
tical standpoint.  Second  Thousand.  8vo,  cloth,  336  illus..ne£,  $2.00 

MOSES,   ALFRED    J.      The  Characters  of  Crystals. 

An  Introduction  to  Physical  Crystallography,  containing  321  Illustra- 
tions and  Diagrams.  8vo,  211  pp net,  $2.00 

MOSS,  SANFORD  A.      The  Lay-out  of  Corliss  Valve 

Gears.  ( Van  JVostrand's  Science  Series,  No.  119).  16mo,  cloth, 
illustrated $0.50 

MTJLLIN,  JOSEPH  P.,  M.E.      Modern  Moulding  and 

Pattern-Making.  A  Practical  Treatise  upon  Pattern-Shop  and  Foun- 
dry Work  :  embracing  the  Moulding  of  Pulleys,  Spur  Gears,  Worm 
Gears,  Balance-Wheels,  Stationary  Engine  and  Locomotive  Cylinders, 
Globe  Valves,  Tool  Work,  Mining  Machinery,  Screw  Propellers,  Pat- 
tern-Shop Machinery,  and  the  latest  improvements  in  English  and 
American  Cupolas ;  together  with  a  large  collection  of  original  and 
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Office,  Pattern-Shop  and  Foundry.  12mo,  cloth,  illustrated. . .  .$2.50 


30  D.  VAN  NOSTKAND  COMPANY'S 


MUNRO,   JOHN,  C.E.,  and  JAMIESON,  ANDREW, 

C.  E.  A  Pocketbook  of  Eiectrical  Rules  and  Tables  for  the 
use  of  Electricians  and  Engineers.  Fifteenth  edition,  revised 
and  enlarged.  With  numerous  diagrams.  Pocket  size.  Leather.  $2. 50 

MURPHY,  J.  G.,  M.E.      Practical  Mining.     A  Field 

Manual  for  Mining  Engineers.  With  Hints  for  Investors  in  Mining 
Properties.  16mo,  morocco  tucks $1.00 

NAQUET,  A.  Legal  Chemistry.  A  Guide  to  the  Detec- 
tion of  Poisons,  Falsification  ( »f  Writings,  Adulteration  of  Alimentary 
and  Pharmaceutical  Substances,  Analysis  of  Ashes,  and  examination  of 
Hair,  Coins,  Arms,  and  Stains,  as  applied  to  Chemical  Jurisprudence, 
for  the  use  of  Chemists,  Physicians,  Lawyers,  Pharmacists  and  Experts. 
Translated,  with  additions,  including  a  list  of  books  and  memoirs  on 
Toxicology,  etc. ,  from  the  French,  by  J.  P.  Battershall,  Ph.  D. ,  with  a 
preface  by  C.  F.  Chandler,  Ph.D.,  M.D.,  LL.D.  12mo,  cloth.  .$2.00 

NASMITH,  JOSEPH,    The  Student's  Cotton  Spinning. 

Third  edition,  revised  and  enlarged.  8vo,  cloth,  622  pages,  250 
illustrations $3.00 

NEUBURGER,  HENRY  and  HENRI  NOALHAT. 

Technology  of  Petroleum.  The  Oil  Fields  of  the  World  ;  their  His- 
tory, Geography  and  Geology.  Annual  Production,  Prospection  and 
Development.  Oil-well  Drilling,  Transportation  of  Petroleum  by 
land  and  sea.  Storage  of  Petroleum.  With  153  illustrations  and  25 
plates.  Translated  from  the  French  by  John  Geddes  Mclntosh.  8vo, 
cloth,  illustrated net,  $10.00 

NEWAliL.,  JOHN  W.     Plain  Practical  Directions  for 

Drawing,  Sizing  and  Cutting  Bevel-Gears,  showing  how  the  Teeth 
may  be  cut  in  a  Plain  Milling  Machine  or  Gear  Cutter  so  as  to  give 
them  a  correct  shape  from  end  to  end  ;  and  showing  how  to  get  out 
all  particulars  for  the  Workshop  without  making  any  Drawings. 
Including  a  Full  Set  of  Tables  of  Eeference.  Folding  Plates.  ,  8vo, 
cloth $1.50 

NEWLANDS,  JAMES.     The  Carpenters'  and  Joiners' 

Assistant :  being  a  Comprehensive  Treatise  on  the  Selection,  Prepara- 
tion and  Strength  of  Materials,  and  the  Mechanical  Principles  of 
Framing,  with  their  application  in  Carpentry,  Joinery,  and  Hand- 
Railing  ;  also,  a  Complete  Treatise  on  Sines ;  and  an  illustrated  Glos- 
sary of  Terms  used  in  Architecture  and  Building.  Illustrated.  Folio, 
half  morocco $15. 00 

NIPHER,   FRANCIS  E.,  A.M.      Theory  of  Magnetic 

Measurements,  with  an  appendix  on  the  Method  of  Least  Squares. 
12mo,  cloth $1.00 

NUGENT,  E.   Treatise  on  Optics;   or,  Light  and  Sight 

theoretically  and  practically  treated,  with  the  application  to  Fine  Art 
and  Industrial  Pursuits.  With  103  illustrations.  12mo,  cloth. .  .$1.50 


SCIENTIFIC  PUBLICATIONS.  31 


O'CONNOR,  HENRY.      The  Gas   Engineer's    Pocket 

Book.  Comprising  Tables,  Notes  and  Memoranda;  relating  to  the 
Manufacture,  Distribution  and  Use  of  Coal  Gas  and  the  Construc- 
tion of  Gas  Works.  Second  edition,  revised.  12mo,  full  leather,  gilt 
edges $3.50 

OLSEN,  Prof.  J.  C.  Quantitative  Chemical  Analysis. 
In  Press. 

OSBORN,  FRANK  C.     Tables  of  Moments  of  Inertia, 

and  Squares  of  Radii  of  Gyration;  Supplemented  by  others  on  the 
Ultimate  and  Safe  Strength  of  Wrought  Iron  Columns,  Safe  Strength 
of  Timber  Beams,  and  Constants  for  readily  obtaining  the  Shearing 
Stresses,  Reactions,  and  Bending  Moments  in  Swing  Bridges.  12mo, 
leather $3.00 

OSTERBERG,  MAX.     Synopsis  of  Current  Electrical 

Literature,  compiled  from  Technical  Journals  and  Magazines  during 
1895.  8vo,  cloth $1.00 

OTJDIN,  Maurice  A.      Standard  Polyphase  Apparatus 

and  Systems.  With  many  diagrams  and  figures.  Third  edition, 
thoroughly  revised.  Fully  Illustrated $3.00 

PALAZ,  A.,  ScD.  A  Treatise  on  Industrial  Photome- 
try, with  special  application  to  Electric  Lighting.  Authorized  trans- 
lation from  the  French  by  George  W.  Patterson,  Jr.  Second  edition, 
revised.  8vo,  cloth.  Illustrated $4.00 

PARR,  G.  D.  A.      Electrical  Engineering   Measuring 

Instruments,  for  Commercial  and  Laboratory  Purposes.  With  370 
diagrams  and  engravings.  8vo,  cl.,  illustrated.  328  pp net,  $3.50 

PARRY,  ERNEST  J.,  B.  Sc.  The  Chemistry  of  Essen- 
tial Oils  and  Artificial  Perfumes.  Being  an  attempt  to  group  together 
the  more  important  of  the  published  facts  connected  with  the  subject ; 
also  giving  an  outline  of  the  principles  involved  in  the  preparation  and 
analysis  of  Essential  Oils.  With  numerous  diagrams  and  tables. 
8vo,  cloth,  illustrated net.  $5.00 

PARRY,  LEONARD  A.,  M.  D.     The  Risks  and  Dan- 

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PARRY,  E.  J.  and  J.  H.  COSTE.  Chemistry  of  Pig- 
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PARSHALL,  H.  F.,  and  HOB  ART,  H.  M.     Armature 

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32  D.  VAN  NOSTRAND  COMPANY'S 


PARSHALL,  H.  F.,  and  EVAN  PARRY.     Electrical 

Equipment  of  Tramways (In  Press.) 

PATERSON,  DAVID,  F.  C.  S.     The  Color  Printing  of 

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Colour  Matching  on  Textiles;  a  Manual  intended 

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PATTEN",  J.    A  Plan  for  Increasing  the  Humidity  of 

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PAULDING,  CHAS.  P.    The  Loss  of  Heat  from  Cov- 
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PEIRCE,   B.      System    of  Analytic    Mechanics.    4to, 
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PERRY,  JOHN.      Applied  Mechanics.      A  Treatise  for 

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PHILLIPS,    JOSHUA.      Engineering    Chemistry.     A 

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PICKWORTH,  CHAS.  N.      The  Indicator  Hand  Book. 

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SCIENTIFIC  PUBLICATIONS.  33 


PICKWORTH,  CHAS.  N.   The  Slide  Rule.    A  Practical 

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PLATTNER'S  Manual  of  Qualitative  and  Quantitative 

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Kolbeck.  Illustrated  with  87  woodcuts.  463  pages.  8vo,  cloth. 
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PLYMPTON,  Prof.  GEO.  W.    The  Aneroid  Barometer: 

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Morocco, $1.00 

POCKET  LOGARITHMS,  to  Four  Places  of  Decimals, 

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gents to  Single  Minutes.  To  which  is  added  a  Table  of  Natural 
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POPE,  F.  L.  Modern  Practice  of  the  Electric  Tele- 
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POPPLE  WELL,  W.  C.    Elementary  Treatise  on  Heat 

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Prevention  of  Smoke,  combined  with  the  Economi- 
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POWLES,   H.  H.     Steam  Boilers (In  Press.) 

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34  D.  VAN  NOSTEAND  COMPANY'S 


PRAY,  Jr.,  THOMAS.  Steam  Tables  and  Engine  Con- 
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Practical  Compounding  of  Oils,  Tallow  and  Grease,  for 

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PRACTICAL  IRON  FOUNDING.      By  the  author  of 

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PREECE,  W.  H.    Electric  Lamps (In  Press.) 

PRELINI,  CHARLES.,  C.  E.  Tunneling;   a  Practical 

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Earth    and   Rock   Excavations.     A    Manual   for 

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PREECE,  W.  H.,  and  STTJBBS,  A.  T.  Manual  of  Tele- 
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PREMIER  CODE.     (See  Hawke,  Wm.  H.) 
PRESCOTT,  Prof.  A.  B.    Organic  Analysis.    A  Manual 

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PRITCHARD,   O.   G.      The    Manufacture    of   Electric 

Light  Carbons.     Illustrated.     8vo,  paper $0.60 


SCIENTIFIC  PUBLICATIONS.  35 


PULLEN,  W.  W.  F.    Application  of  Graphic  Methods 

to  the  Design  of  Structures.  Specially  prepared  for  the  use  of  En- 
gineers. A  Treatment  by  Graphic  Methods  of  t lie  Forces  and  Princi- 
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Chimneys  and  Masonry  Structures.  12mo,  cloth.  Profusely  Illus- 
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PTJLSIFER,  W.  H.     Notes  for  a  History  of  Lead.  8vo, 

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PUTSCH,  ALBERT.      Gas  and  Coal  Dust  Firing;   a 

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purpose  since  1885.  With  diagrams  and  figures.  Translated  from 
the  German  by  Charles  Salter.  8vo,  cloth,  illustrated. . .  .net,  $3.00 

PYNCHON,    Prof.    T.  R.     Introduction  to    Chemical 

Physics,  designed  for  the  use  of  Academies,  Colleges,  and  High 
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RADFORD,   Lieut.  CYRUS.  S.    Handbook  on  Naval 

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RAFTER,    GEO.    W.      Treatment   of  Septic    Sewage 

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RAM,  GILBERT  S.    The  Incandescent  Lamp  and  its 

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RAND  ATI,    PAUL.       Enamels    and   Enamelling;    an 

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36  D.  VAN  NOSTRAND  COMPANY'S 


gold  and  silver,  and  manufacturers  of  objects  of  art.  Third  German 
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RANKINE,  W.  J.  MACQUORN.     Applied  Mechanics. 

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Useful  Rules  and  Tables  for  Engineers  and  Others. 

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RAPHAEL,  P.  C.     Localization  of  Faults  in  Electric 

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SCIENTIFIC  PUBLICATIONS.  37 


well  as  the  most  costly  Cyrstal  and  Ruby.  British  manufacturers  have 
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REED'S    ENGINEERS'   HAND-BOOK,  to  the  Local 

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Useful  Hints  to  Sea-going  Engineers,  and  How  to 

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REINHARDT,  CHAS.  W.     Lettering  for  Draftsmen, 

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REISER,  F.      Hardening  and  Tempering  of  Steel,  in 

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N.    Faults  in  the  Manufacture  of  Woolen  Goods, 

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RICE,  J.   M.,  and   JOHNSON,  W.   W.       On  a  New 

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RIPPER,    WILLIAM.      A  Course  of   Instruction   in 

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ROBERTSON,  L.  S.     Water-tube  Boilers.     Based  on 

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ROSE,  JOSHUA,  M.E.  The  Pattern-Makers'  Assistant. 

Embracing  Lathe  Work,  Branch  Work,  Core  Work,  Sweep  Work,  and 
Practical  Gear  Constructions,  the  Preparation  and  Use  of  Tools, 
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Key  to  Engines  and  Engine-running.    A  Practical 

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Engine  Adjustments,  and  other  Valuable  Information  necessary  for 
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ROWAN,  FREDERICK  J.      The  Practical  Physics  of 

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SABINE,   ROBERT.      History    and    Progress    of   the 

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SAELTZER,  ALEX.    Treatise  on  Acoustics  in  connec- 
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SCIENTIFIC  PUBLICATIONS.  39 


SALOMONS,  Sir  DAVID,  M.A.    Electric-Light  Instal- 

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SANFORD,  P.  GERALD.  Nitro-Explosives.  A  Prac- 
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SAUNDERS,  CHARLES  H.      Handbook  of  Practical 

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SATJNNIER,  CLATJDIUS.     Watchmaker's  Handbook. 

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SCHELLEN,  Dr.  H.  Magneto-Electric  and  Dynamo- 
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SCHUMANN,  F.  A  Manual  of  Heating  and  Ventilation 

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40  D.  VAN  NOSTRAND  COMPANY'S 


SEATON,  A.   E.    A  Manual  of  Marine  Engineering. 

Comprising  the  Designing,  Construction  and  Working  of  Marine 
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and  ROTJNTHWAITE,  H.  M.  A  Pocketbook  of  Ma- 
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SEELIGMANN,  T.,  TOKRILHON,  G.   L.,   and  FAL- 

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SEWAlili,  C.  H.  Wireless  Telegraphy.  With  Diagrams 
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SEWEliL,   T.     Elements  of  Electrical  Engineering: 

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Chemistry  of  the  Materials  of  Engineering;  A 

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SHAW,  SIMEON.      The  History  of  the  Staffordshire 

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SCIENTIFIC  PUBLICATIONS.  41 


SHAW,  (Liieut.-Col.)  WM.  J.     Studies  in  Map  Reading 

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Tactical  Operations  for  Field  Officers ;  being  up-to- 
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SHELDON,  Prof.  S.,  Ph.  D.,  and  HOB  ART,  MASON, 

B.  S.  Dynamo  Electric  Machinery  ;  Its  Construction,  Design  and 
Operation.  Direct  Current  Machines.  Second  edition.  8vo,  cloth, 
illustrated net.  $2.50 

Alternating  Current  Machines  ;  being  the  second 

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SHIELDS,  J.  E.  Notes  on  Engineering  Construction. 

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of  the  Material  employed  in  Tunnelling,  Bridging,  Canal  and  Road 
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SHOCK,  WM.  H.  Steam  Boilers,  Their  Design,  Con- 
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Engineers.  87  woodcut  illus.  Fourth  edition.  8vo,  cloth $3.50 

SHTJNK,  W.  F.   The  Field  Engineer.    A  Handy  Book 

of  practice  in  the  Survey,  Location,  and  Truck-work  of  Railroads,  con- 
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SIMMS,  F.  W.  A  Treatise  on  the  Principles  and  Prac- 
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Practical    Tunneling.      Fourth    Edition,    Revised 

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Eractice  by  D.  Kinnear  Clark.    With  36  plates  and  other  illustrations, 
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42  D.  VAN  NOSTBAND  COMPANY'S 


SIMPSON,    GEORGE.      The    Naval    Constructor.      A 

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SLATER,  J.  W.     Sewage  Treatment,  Purification,  and 

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SMITH,  ISAAC  W.,  C.E.      The  Theory  of  Deflections 

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SMITH,  J.  CRUICKSHANK.    Manufacture  of  Paint; 

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SNELli,  ALBION  T.     Electric  Motive   Power:     The 

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to  Mining  Work.  Second  edition.  8vo,  cloth,  illustrated $4.00 

SOXHLET,  D.  H.    Art  of  Dyeing  and  Staining  Marble, 

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sorts  of  Wood.  A  Practical  Hand-book  for  the  use  of  Joiners,  Tur- 
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SPA.NG,  HENRY  W.  A  Practical  Treatise  on  Light- 
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SPEYERS,   CLARENCE  L.    Text  Book  of  Physical 

Chemistry.      8vo,  cloth $2.25 

STAHL,  A.  W.,  and  A.  T.  WOODS.  Elementary  Me- 
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STALEY,  CADY,  and  PIERSON,  GEO.  S.  The  Separ- 
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STAND  AGE,  H.  C.    Leatherworkers'  Manual :  being  a 

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SCIENTIFIC  PUBLICATIONS.  43 


STEWART,  R.  W.    A  Text  Book  of  Light.    Adapted 

to  the  Kequirements  of  the  Intermediate  Science  and  Preliminary 
Scientific  Examinations  of  the  University  of  London,  and  also  for 
General  Use.  Numerous  Diagrams  and  Examples.  12 mo,  cloth,  $1.00 

A  Text  Book  of  Heat.  Illustrated.  8vo,  cloth... .$1.00 

A    Text-Book    of    Magnetism    and    Electricity. 

160  illus.  and  Numerous  Examples.    12mo,  cloth $1.00 

An    Elementary    Text-book    of    Magnetism    and 

Electricity.     With  numerous  figures  and  diagrams.    12mo,  cloth  $1.00 

STONE,    ROY,    GENERAL.     New   Roads  and   Road 

Laws  in  the  United  States.  200  pages,  with  numerous  illustrations. 
12mo,  cloth $1.00 

STILES,  AMOS.   Tables  for  Field  Engineers.  Designed 

for  use  in  the  field.  Tables  containing  all  the  functions  of  a  one 
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required  degree.  Also,  Tables  of  Natural  Sines  and  Tangents.  12mo, 
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STILLMAN,  PAUL.     Steam-Engine  Indicator  and  the 

Improved  Manometer  Steam  and  Vacuum  Gauges ;  their  Utility  and 
Application.  New  edition.  12mo,  flexible  cloth $1.00 

STONEY,   B.  D.    The  Theory  of  Stresses  in  Girders 

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STUART,  C.  B.  U.  S.  N.      Lives  and  Works  of  Civil 

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The   Naval   Dry  Docks  of  the  United   States. 

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SUFFLING,    E.    R.      Treatise    on   the  Art  of  Glass 

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SWEET,  S.  H.     Special  Report  on  Coal,  showing  its 

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SWOOPE,  C.  WALTON.      Practical  Lessons  in  Efec- 

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TAILFER,  L.    Practical  Treatise  on  the  Bleaching  of 

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Translated  from  the  French  by  John  Geddes  Mclntosh.  8vo,  cloth, 
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TEMPLETON,  WM.  The  Practical  Mechanic's  Work- 
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Eevised  and  enlarged  by  W.  S.  Hutton.  12mo,  morocco .$2.00 

TESLA,  N.    Experiments  with  Alternate  Currents  of 

High  Potential  and  High  Frequency.  A  Lecture  delivered  before  the 
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biographical  sketch  of  the  author.  With  figures  and  diagrams. 
12mo,  cloth,  illustrated.  New  Edition.  In  Press. 

THOM,  CHAS.,  and  WILLIS  H.  JONES.    Telegraphic 

Connections:  embracing  Kecent  Methods  in  Quadruplex  Telegraphy. 
20  full  page  plates,  some  colored.  Oblong,  8vo,  cloth $1.50 

THOMAS,  C.  W.  Paper  Makers'  Handbook ;  a  Prac- 
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THOMPSON,  EDWARD  P.,  M.  E.  How  to  Miake  In- 
ventions ;  or,  Inventing  as  a  Science  and  an  Art.  A  Practical  Guide 
for  Inventors.  Second  edition.  8vo,  boards , $1.00 

Roentgen  Rays  and  Phenomena  of  the  Anode  and 

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50  Diagrams,  40  Half-tones.  8vo,  cloth $1.50 

THORNLEY,  T.      Cotton  Combing  Machines.     With 

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343  pages net,  $3.00 

Contents. — Preface,  List  of  Illustrations;  The  Silver  Lap  Ma- 
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Various  Calculations  ;  Various  Notes  and  Discussions ;  Cotton  Comb- 
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TODD,  JOHN  and  W.  B.  WHALL.  Practical  Seaman- 
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SCIENTIFIC  PUBLICATIONS.  4=5 


TOOTHED  GEARING.       A  Practical  Hand-Book  for 

Offices  and  Workshops.  By  a  Foreman  Patternmaker.  184  Illustra- 
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TRATMAN,   E.   E.   RUSSELL.     Railway  Track  and 

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Table  Book.)  Van  JVostrand's /Science  Series.  16mo,  cloth ...  .50 
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TRE VERT,  EDWARD.    How  to  build  Dynamo-Electric 

Machinery,  embracing  Theory  Designing  and  Construction  of  Dy- 
namos and  Motors.  With  appendices  on  Field  Magnet  and  Armature 
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Wire  Gauges.  Illustrated.  8vo,  cloth $2.50 

Electricity  and  its  Recent  Applications.  A  Practi- 
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TUCKER,  Dr.  J.  H.  A  Manual  of  Sugar  Analysis,  in- 
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Sugar,  Dextrose,  Levulose,  and  Milk  Sugar.  8vo,  cloth,  illus- 
trated  $3.50 

TUMLIRZ,  Dr.  O.      Potential  and  its  Application  to 

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lated from  the  German  by  D.  Robertson.  HI.  12mo,  cloth. . .  .$1.25 

TTJNNER,  P.      A.    Treatise  on    Roll-Turning  for  the 

Manufacture  of  Iron.  Translated  and  adapted  by  John  B.  Pearse,  of 
the  Pennsylvania  Steel  Works,  with  numerous  engravings,  woodcuts. 
8vo,  cloth,  with  folio  atlas  of  plates $10.00 

UNDERBILL,  CHAS.  R.      The  Electro-Magnet.    New 

and  revised  edition In  Press. 

URQTJHART,  J.  W.  Electric  Light  Fitting.  Embody- 
ing Practical  Notes  on  Installation  Management.  A  Hand-book  for 
Working  Electrical  Engineers.  With  numerous  illustrations.  12mo, 
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SCIENTIFIC  PUBLICATIONS.  47 


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Catalogue  of  the  Van  Nostrand 

Science  Series. 


are  put  up  in  a  uniform,  neat,  and  attractive  form. 
J-      boards.     Price  50  cents  per  volume.      The   subjects  are  of  an 
eminently  scientific  eharaoter,  and  embrace  a  wide  range  of  topics,  and 
are  amply  illustrated  when  the  subject  demands. 

No.  x.  CHIMNEYS  FOR  FURNACES  AND  STEAM-BOILERS. 

By  R.  Armstrong,  C.E.  Third  American  edition,  revised  and  partly 
rewritten,  with  an  appendix  on  Theory  of  Chimney  Draught,  by  F.  E. 
Idell,  M.E. 

No.  2.     STEAM-BOILER  EXPLOSIONS.    By  Zerah  Colburn.     N«w 
edition,  revised  by  Prof.  R.  H.  Thurston. 


No.  3.     PRACTICAL    DESIGNING    OF     RETAINING- WALLS. 

By 

W.  Cain. 


Arthur  Jacob,  A.B.     Second  edition,  revised,  with  additions  by  Prof, 


No.  4.  PROPORTIONS  OF  PINS  USED  IN  BRIDGES.  Second 
edition,  with  appendix.  By  Charles  E.  Bender,  C.E. 

No.  5.  VENTILATION  OF  BUILDINGS.  By  W.  F.  Butler.  Second 
edition,  re-edited  and  enlarged  by  James  L.  Greenleaf,  C.E. 

No.  6.     ON     THE     DESIGNING     AND     CONSTRUCTION      OF 

STORAGE   RESERVOIRS.     By  Arthur  Jacob,  A.B.     Second  edition, 
revised,  with  additions  by  E.  Sherman  Gould. 

No.  7.  SURCHARGED  AND  DIFFERENT  FORMS  OF  RE- 
TAINING-WALLS.  By  James  S.  Tate,  C.E. 

No.  8.    A  TREATISE  ON  THE  COMPOUND  ENGINE.     By  John 

Turnbull,  jun.     Second  edition,  revised  by  Prof.  S.  W.  Robinson. 

No.  9.  A  TREATISE  ON  FUEL.  By  Arthur  V.  Abbott,  C.  E. 
Founded  on  the  original  treatise  of  C.  William  Siemens,  D.C.L. 

No.  10.  COMPOUND  ENGINES.  Translated  from  the  French  of  A. 
Mallet.  Second  edition,  revised,  with  Results  of  American  Practice,  by 
Richard  H.  Buel,  C.E. 

No.  ii.     THEORY  OF  ARCHES.     By  Prof.  W.  Allan. 

No.  12.  A  THEORY  OF  VOUSSOIR  ARCHES.  By  Prof.  W.  E. 
Cain.  Second  edition,  revised  and  enlarged.  Illustrated. 

No.  13.  GASES  MET  WITH  IN  COAL-MINES.  By  J.  J.  Atkinson. 
Third  edition,  levised  and  enlarged  by  Edward  H  Williams,  jun. 


D.   VAN  NOSTRAND  COMPANY'S 


No.  14.     FRICTION  OF  AIR  IN  MINES.    By  J.  J.  Atkinson. 
No.  15.     SKEW   ARCHES.     By  Prof.  E.  W.  Hyde,  C.E.     Illustrated. 
No.  16.    A  GRAPHIC  METHOD  OF  SOLVING  CERTAIN  QUES- 
TIONS IN  ARITHMETIC  OR  ALGEBRA.     By  Prof.  Geo.  L.  Vose. 

No.  17.     WATER  AND  WATER-SUPPLY.     By  Prof.  W.  H.  Corfield 

of  the  University  College,  London. 

No.  18.     SEWERAGE    AND     SEWAGE    PURIFICATION.      By 

M.  N.  Baker,  Assoc.  Ed.  Engineering  News. 

No.  19.     STRENGTH     OF      BEAMS      UNDER     TRANSVERSE 

LOADS.    By  Prof.  W.  Allan,  author  of  "Theory  of  Arches." 

No.  20.     BRIDGE    AND    TUNNEL    CENTRES.      By  John   B.   Mo- 
Master,  C.E. 

No.  21.     SAFETY  VALVES.     By  Richard  H.  Buel,  C.E.  Third  edition. 
No,  22.     HIGH    MASONRY    DAMS.     By  E.  Sherman  Gould,  C.E. 

No.  23.  THE  FATIGUE  OF  METALS  UNDER  REPEATED 

STRAINS.  With  Various  Tables  of  Results  and  Experiments.  From 
the  German  of  Prof.  Ludwig  Spangenburgh,  with  a  Preface  by  S.  H. 
Shreve,  A.M. 

No.  24.  A  PRACTICAL  TREATISE  ON  THE  TEETH  OF 

WHEELS.     By  Prof.  S.  W.  Robinson.     Second  edition,  revised. 

No.  25.     ON    THE   THEORY  AND   CALCULATION    OF  CON- 
TINUOUS BRIDGES.    By  R.  M.  Wilcox,  Ph.B. 

No.  26.     PRACTICAL    TREATISE  ON   THE   PROPERTIES  OF 

CONTINUOUS   BRIDGES.     By  Charles  Bender,  C.E. 

No.  27.     ON     BOILER     INCRUSTATION      AND     CORROSIOH 

By  F.  J.  Rowan.     New  edition,  revised  and  partly  rewritten  by  F.  L. 
Idell,  M.  E. 
No.  28.     TRANSMISSION      OF     POWER     BY     WIRE     ROPES 

By  Albert  W.  Stahl,  U.S.N.     Second  edition. 

No.  29.     STEAM        INJECTORS.       Translated    from     the     French    oi 
M.  Leon  Pochet. 

No.  30.     TERRESTRIAL   MAGNETISM,   AND   THE    MAGNET- 
ISM   OF   IRON   VESSELS.     By  Prof.  Fairman  Rogers. 

1*0.31.      THE      SANITARY      CONDITION     OF      DWELLING- 
HOUSES   IN   TOWN  AND  COUNTRY.     By  George  E.  Waring,  jun. 

No.  32.     CABLE-MAKING    FOR    SUSPENSION    BRIDGES.     By 
W.  Hildenbrand,  C.E. 

No.  33.     MECHANICS   OF   VENTILATION.     By  George  W.  Rafter, 
C.E.     New  edition  (1895),  revised  by  author. 

No.  34.     FOUNDATIONS.      By  Prof.  Jules   Gaudard,  C.E.      Translated 
from  the  French. 

No.  35.     THE     ANEROID     BAROMETER  :      ITS     CONSTRUC- 
TION AND  USE.     Compiled  by  George  W.  Plympton.  Eighth  edition. 

No.  36.     MATTER* AND    MOTION.      By  J.  Clerk   Maxwell,    M.A. 
^Second  American  edition. 


SCIENCE  SERIES. 


No.  37.  GEOGRAPHICAL  SURVEYING:  ITS  USES,  METH- 
ODS, AND  RESULTS.  By  Frank  De  Yeaux  Carpenter,  C.E. 

No.  38.    MAXIMUM    STRESSES    IN    FRAMED    BRIDGES.     By 

Prof.  William  Cain,  A.M.,  C.E.    New  and  revised  edition. 
No.  39.    A      HANDBOOK      OF      THE      ELECTRO-MAGNETIC 

TELEGRAPH.     By  A.  E.  Loring.    New  enlarged  edition. 
No.  40.     TRANSMISSION  OF  POWER  BY  COMPRESSED  AIR. 

By  Robert  Zahner,  M.E.    Second  edition. 
No.  41.     STRENGTH  OF  MATERIALS.    By  William  Kent,  C.E., 

Assoc.  Ed.  Engineering  News. 
No.  42.    THEORY    OF    STEEL-CONCRETE    ARCHES    AND 

OF  VAULTED  STRUCTURES.     By  Prof.  William  Cain. 
No.  43.    WAVE   AND  VORTEX   MOTION.    By  Dr.  Thomas  Craig  of 

Johns  Hopkins  University. 
No.  44.     TURBINE   WHEELS.     By  Prof.  W.  P.  Trowbridge,  Columbia 

College.     Second  edition. 

No.  45.  THERMODYNAMICS.  By  Prof.  H.  T.  Eddy,  University  of 
Cincinnati. 

No.  46.  ICE-MAKING  MACHINES.  New  edition,  revised  and  en- 
larged  by  Prof.  J.  E.  Denton.  From  the  French  of  M.  Le  Doux. 

No.  47.  LINKAGES;  THE  DIFFERENT  FORMS  AND  USES 
OF  ARTICULATED  LINKS.  By  J.  D.  C.  de  Roos. 

No.  48.     THEORY    OF    SOLID    AND    BRACED    ARCHES.      By 

William  Cain,  C.E. 

No.  49.     ON    THE    MOTION    OF    A    SOLID   IN    A    FLUID.    By 

Thomas  Craig,  Ph.D. 

No.  50.  DWELLING-HOUSES  :  THEIR  SANITARY  CON- 
STRUCTION AND  ARRANGEMENTS.  By  Prof.  W.  H.  Corfield. 

No.  51.     THE    TELESCOPE  :    ITS    CONSTRUCTION,  ETC.    By 

Thomas  Nolan. 

No.  52.  IMAGINARY  QUANTITIES.  Translated  from  the  French  of 
M.  Argand.  By  Prof.  Hardy. 

No.  53.     INDUCTION  COILS  :  HOW  MADE  AND  HOW  USED. 

Third  American,  from  Ninth  English  edition. 

No.  54.  KINEMATICS  OF  MACHINERY.  By  Prof.  Kennedy.  With 
an  introduction  by  Prof.  R.  H.  Thurston. 

No.  55.    SEWER  GASES  :  THEIR  NATURE  AND  ORIGIN.    By 

A.  de  Varona. 

No.  56.  THE  ACTUAL  LATERAL  PRESSURE  OF  EARTH- 
WORK. By  Benjamin  Baker,  M.  Inst  C.E. 

No.  57.  INCANDESCENT  ELECTRIC  LIGHTING.  A  Practical 
Description  of  the  Edison  System.  By  L.  H.  Latimer,  to  which  is 
added  the  Design  and  Operation  of  Incandescent  Stations,  by  C.  J. 
Field,  and  the  Maximum  Efficiency  of  Incandescent  Lamps,  by  John 
W.  Ho  well. 

No.  58-  ,  THE  VENTILATION  OF  COAL-MINES.  By  W.  Fairley. 
M.E  ,  F.S.S. 


D.   VAN  NOSTRAND  COMPANY'S 


No.  59.  RAILROAD  ECONOMICS ;  OR,  NOTES,  WITH  COM- 
MENTS. By  S.  W.  Robinson,  C.E. 

No.  60.  STRENGTH  OF  WROUGHT-IRON  BRIDGE  MEM- 
BERS.  By  S.  W.  Robinson,  C.E. 

No.  61.  POTABLE  WATER  AND  METHODS  OF  DETECT- 
ING IMPURITIES.  By  M.  N.  Baker,  Ph.B. 

No.  62.  THE  THEORY  OF  THE  GAS-ENGiNE.  By  Dugald  Clerk. 
Second  edition.  With  additional  matter.  Edited  by  F.  E.  Idell,  M.E. 

No.  63.  HOUSE  DRAINAGE  AND  SANITARY  PLUMBING. 
By  W.  P.  Gerhard.  Eighth  edition,  revised. 

No.  64.     ELECTRO-MAGNETS.  By  A.  N.  Mansfield,  S.B. 

No.  65.  POCKET  LOGARITHMS  TO  FOUR  PLACES  OF  DECI- 
MALS. 

No.  66.  DYNAMO-ELECTRIC  MACHINERY.  By  S.  P.  Thompson, 
With  notes  by  F.  L.  Pope.  Third  edition. 

No.  67.  HYDRAULIC  TABLES  BASED  ON  "  KUTTER'S 
FORMULA."  By  P.  J.  Flynn. 

No.  68.  STEAM-HEATING.  By  Robert  Briggs.  Third  edition,  revised, 
with  additions  by  A.  R.  Wolff. 

No.  69.  CHEMICAL  PROBLEMS.  By  Prof.  J.  C.  Foye.  Fourth 
edition,  revised  and  enlarged. 

No.  70.  EXPLOSIVE  MATERIALS.  The  Phenomena  and  Theories 
of  Explosion,  and  the  Classification,  Constitution  and  Preparation  of 
Explosives.  By  First  Lieut.  John  P.  Wisser,  U.S.A. 

No.  71.  DYNAMIC  ELECTRICITY.  By  John  Hopkinson,  J.  N. 
Shoolbred,  and  R.  E.  Day. 

No.  72.  TOPOGRAPHICAL  SURVEYING.  By  George  J.  Specht, 
Prof.  A.  S.  Hardy,  John  B.  McMaster,  and  H.  F.  Walling. 

No.  73.  SYMBOLIC  ALGEBRA;  OR,  THE  ALGEBRA  OF 

ALGEBRAIC  NUMBERS.     By  Prof.  W.  Cain. 

No.  74.     TESTING     MACHINES:      THEIR     HISTORY,      CON- 

STRUCTION,  AND  USE.     By  Arthur  V.  Abbott. 

No.  75.  RECENT  PROGRESS  IN  DYNAMO-ELECTRIC  MA- 
CHINES. Being  a  Supplement  to  Dynamo-Electric  Machinery.  By 
Prof.  Sylvanus  P.  Thompson. 

No.  76.  MODERN  REPRODUCTIVE  GRAPHIC  PROCESSES. 

By  Lieut.  James  S.  Pettit,  U.S.A. 

No.  77.  STADIA  SURVEYING.  The  Theory  of  Stadia  Measurements. 
By  Arthur  Winslow. 

No.  78.  THE  STEAM-ENGINE  INDICATOR,  AND  ITS  USE. 
By  W.  B.  Le  Van. 

No.  79.     THE  FIGURE  OF  THE  EARTH.     By  Frank  C.  Roberts, C.E. 

No.  80.  HEALTHY  FOUNDATIONS  FOR  HOUSES.  By  Gleon 
Brown. 


SCIENCE  SERIES. 


No.  8z.     WATER      METERS  :       COMPARATIVE      TESTS     OF 

ACCURACY,  DELIVERY,   ETC.     Distinctive  features  of  the  Worth- 
ington,  Kennedy,  Siemens,  and  Hesse  meters.     By  Ross  E.  Browne. 

No.  82.     THE    PRESERVATION    OF    TIMBER    BY    THE   USE 

OF  ANTISEPTICS.     By  Samuel  Bagster  Boulton,  C.E. 

No.  83.  MECHANICAL  INTEGRATORS.  By  Prof.  Henry  S.  H. 
Shaw,  C.E. 

No.  84.  FLOW  OF  WATER  IN  OPEN  CHANNELS,  PIPES, 
CONDUITS,  SEWERS,  ETC.  With  Tables.  By  P.  J.  Flynn,  C.E. 

No.  85.     THE  LUMINIFEROUS  ^THER.     ByProf.de  Volson  Wood. 

No.  86.  HAND-BOOK  OF  MINERALOGY;  DETERMINATION 
AND  DESCRIPTION  OF  MINERALS  FOUND  IN  THE  UNITED 
STATES.  By  Prof.  J.  C.  Foye. 

No.  87.  TREATISE  ON  THE  THEORY  OF  THE  CON- 
STRUCTION OF  HELICOIDAL  OBLIQUE  ARCHES.  By  John 
L.  Culley,  C.E. 

No.  88.  BEAMS  AND  GIRDERS.  Practical  Formulas  for  their  Re- 
sistance. By  P.  H.  Philbrick. 

No.  89.  MODERN  "  GUN-COTTON  :  ITS  MANUFACTURE, 
PROPERTIES,  AND  ANALYSIS.  By  Lieut.  John  P.  Wisser,  U.S.A. 

No.  90.  ROTARY  MOTION,  AS  APPLIED  TO  THE  GYRO- 
SCOPE. By  Gen.  J.  G.  Barnard. 

No.  91.  LEVELING:  BAROMETRIC,  TRIGONOMETRIC,  AND 
SPIRIT.  By  Prof.  I.  O.  Baker. 

No.  92.     PETROLEUM  :     ITS     PRODUCTION     AND     USE.      By 

Boverton  Redwood,  F.I.C.,  F.C.S. 

No.  93.  RECENT  PRACTICE  IN  THE  SANITARY  DRAIN- 
AGE OF  BUILDINGS.  With  Memoranda  on  the  Cost  of  Plumbing 
Work.  Second  edition,  revised.  By  William  Paul  Gerhard,  C.  E. 

No.  94.     THE   TREATMENT  OF   SEWAGE.      By  Dr.   C.   Meymott 

Tidy. 

No.  95«  PLATE  GIRDER  CONSTRUCTION.  By  Isami  Hiroi,  C.E, 
Second  edition,  revised  and  enlarged.  Plates  and  Illustrations. 

No.  96.  ALTERNATE  CURRENT  MACHINERY.  By  Gisbert 
Kapp,  Assoc.  M.  Inst.,  C.E. 

No.  97.     THE    DISPOSAL    OF    HOUSEHOLD   WASTE.     By  W. 

Paul  Gerhard,  Sanitary  Engineer. 

No.  98.  PRACTICAL  DYNAMO-BUILDING  FOR  AMATEURS. 
HOW  TO  WIND  FOR  ANY  OUTPUT.  By  Frederick  Walker. 
Fully  illustrated. 

Ho.  oo.  TRIPLE-EXPANSION  ENGINES  AND  ENGINE 
TRIALS.  By  Prof.  Osborne  Reynolds.  Edited,  with  notes,  etc.,  by 
F.  E.  Idell,  M.  E. 


SCIENCE  SERIES. 


No.  100.  HOW  TO  BECOME  AN  ENGINEER  ;  OR,  THE 
THEORETICAL  AND  PRACTICAL  TRAINING  NECESSARY  IN 
FITTING  FOR  THE  DUTIES  OF  THE  CIVIL  ENGINEER.  The 
Opinions  of  Eminent  Authorities,  and  the  Course  of  Study  in  the 
Technical  Schools.  By  Geo.  W.  Plympton,  Am.  Soc.  C.E. 

No.  101.  THE  SEXTANT  AND   OTHER   REFLECTING 

MATHEMATICAL  INSTRUMENTS.  With  Practical  Suggestions 
and  Wrinkles  on  their  Errors,  Adjustments,  and  Use.  With  thirty- 
three  illustrations.  By  F.  R.  Brainard,  U.S.N. 

No.  102.  THE  GALVANIC  CIRCUIT  INVESTIGATED 
MATHEMATICALLY.  By  Dr.  G.  S.  Ohm,  Berlin,  1827.  Translated 
by  William  Francis.  With  Preface  and  Notes  by  the  Editor,  Thomas 
D.  Lockwood,  M.I.E.E. 

No.  103.  THE  MICROSCOPICAL  EXAMINATION  OF  POTA- 
BLE WATER.  With  Diagrams,  By  Geo.  W.  Rafter. 

No.  104.  VAN  NOSTRAND'S  TABLE-BOOK  FOR  CIVIL  AND 
MECHANICAL  ENGINEERS.  Compiled  by  Geo.  W.  Plympton,  C.E, 

No.   105.     DETERMINANTS,  AN   INTRODUCTION  TO  THE 

STUDY  OF.     With  examples.     By  Prof.  G.  A.  Miller. 

No.  106.  TRANSMISSION  BY  AIR-POWER.  Illustrated.  By 
Prof.  A.  B.  W.  Kennedy  and  W.  C.  Unwin. 

No.    107.     A  GRAPHICAL  METHOD   FOR  SWING-BRIDGES. 

A  Rational  and  Easy  Graphical  Analysis  of  the  Stresses  in  Ordinary 
Swing-Bridges.  With  an  Introduction  on  the  General  Theory  of  Graphi- 
cal Statics.  4  Plates.  By  Benjamin  F.  LaRue,  C.E. 

No.    108.     A   FRENCH    METHOD    FOR    OBTAINING   SLIDE- 

VALVE  DIAGRAMS.  8  Folding  Plates.  By  Lloyd  Bankson,  B.S., 
Assist.  Naval  Constructor,  U.S.N. 

No.  109.  THE  MEASUREMENT  OF  ELECTRIC  CURRENTS. 

ELECTRICAL  MEASURING  INSTRUMENTS.  By  Jas.  Swinburne.  METERS 
FOR  ELECTRICAL  ENERGY.  By  C.  H.  Wordingham.  Edited  by 
T.  Commerford  Martin.  Illustrated. 

No.  1 10.  TRANSITION  CURVES.  A  Field  Book  for  Engineers, 
containing  Rules  and  Tables  for  laying  out  Transition  Curves.  By 
Walter  G.  Fox. 

No.  in.  GAS-LIGHTING  AND  GAS-FITTING,  including  Specifica- 
tions and  Rules  for  Gas  Piping,  Notes  on  the  Advantages  of  Gas  for 
Cooking  and  Heating,  and  useful  Hints  to  Gas  Consumers.  Second 
edition,  rewritten  and  enlarged.  By  Wm.  Paul  Gerhard. 

No.  112.  A  PRIMER  ON  THE  CALCULUS.  By  E.  Sherman 
Gould,  C.E. 

No.  113.  PHYSICAL  PROBLEMS  AND  THEIR  SOLUTION. 
By  A.  Bourgougnon,  formerly  Assistant  at  Bellevue  Hospital. 

No.  114.  MANUAL  OF  THE  SLIDE  RULE.  By  F.  A.  Halsey  of 
the  American  Machinist.  Second  edition,  revised. 


SCIENCE   SERIES. 


No.  115.  TRAVERSE  TABLES,  showing  the  difference  of  Latitude 
and  Departure  for  distances  between  i  and  100  and  for  Angles  to 
Quarter  Degrees  between  i  degree  and  90  degrees.  (Reprinted  from 
Scribner's  Pocket  Table  Book.) 

No.  116.  W°RM  AND  SPIRAL  GEARING.  Reprinted  from 
"American  Machinist."  By  F.  A.  Halsey. 


SCIENTIFIC  PUBLICATIONS. 


Catalogue  of  Weale's  Rudimentary 

Scientific  Series. 


i^"  "WEALE'S  SERIES  includes  Text-Books  on  almost  every  branch  of 
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Chemical  Science,  and  many  miscellaneous  Treatises.  The  whole  are  constantly 
undergoing  revision,  and  new  editions,  brought  up  to  the  latest  discoveries  in 
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6.  Mechanics,  byTomlinson 60 

7.  Electricity,  by  Harris 

7*.  Galvanism  and  Electricity,  by  Harris 

8.  Rudimentary  Magnetism,  by  Harris  and  Noad 

11.  Electric  Telegraph,  History,  by  Sabine 

12.  Pneumatics,  Acoustics,  &c. ,  by  Chas.  Tomlinson,  F.  B.  S.  4th  Edition, 

enlarged 60 

16.  Architecture,  Orders,  by  Leeds 60 

17.  Architecture,  Styles,  by  Bury ...     .80 

16.  17,  bound  together 1.40 

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16.  17,  and  18,  in  one  vol.  half-bound 2.40 

20.  Perspective,  by  Pyne 80 

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23.  Brick  and  Tile  Making,  by  Dobson 1.20 

25,  Masonry  and  Stone  Cutting,  by  Dobson 1.00 

31.  Well-Sinking.     By  Swindell  and  Burnell 80 

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A.  T.  WALMISLEY...,  .80 


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35.  Blasting  and  Quarrying,  by  Burgoyne 60 

36.  Dictionary  of  Terms  in  Architecture,  &c.,  by  John  Weale.     Enlarged 

by  Eobert  Hunt,  F.K.S 2.00 

40.   Glass  Staining  and  Painting  on  Glass,  by  Gessert  and  Fromberg 1.00 

42.  Cottage  Building,  by  C.  Bruce  Allen .80 

43.  Tubular  and  Girder  Bridges,  by  Dempsey 80 

44.  Foundations  and  Concrete  Work,  by  Dobson 60 

45.  Limes,  Cements,  Mortars,  <fcc.,  by  Burnell 60 

50.  Law  of  Contracts,  by  Gibbons 

51.  Naval  Architecture,  byPeake 1.40 

53*  Ships,  Construction  of ,  by  Sommerfeldt 60 

53**.  Plates  to  ditto,  4to 3.00 

54.  Masting  and  Rigging,   by  Kipping 80 

54*.  Iron  Ship  Building,  by  Grantham 

55.  Navigation  ("  The  Sailor's  Sea  Book"),  by  Greenwood.    New  Edition 

by  W.  H.  Eosser... 1.00 

57.  Warming  and  Ventilation,  byTomlinson 

59.  Steam  Boilers,  by  Armstrong 60 

60.  Land  and  Engineering  Surveying,  by  Baker 80 

61*  Eeady  Reckoner  for  Land,  by  Arman 80 

67.  Clocks  and  Watches,  and  Bells,  by  Sir  E.  Beckett.        7th  Edition,  re- 
vised and  enlarged 1.80 

69.  Music,  by  .Spencer 1.00 

71.  Pianoforte  Instruction,  by  Spencer 60 

69  &  71.  Music  and  the  Pianoforte,  by  Spencer.     In  1  vol.  half -bound 

72.  Eecent  and  Fossil  Shells,  by  Woodward 

76.  Geometry,  Descriptive,  by  Heather .80 

80.  Marine  Engines,  by  Murray.     8th  Edition,  with  Additions  by  G.  Car- 

lisle, C.E 1.80 

80*  Embanking  Lands  from  the  Sea,  by  Wiggins 

81.  Water  Works,  by  Hughes 1.60 

83**.  Locks,   Construction  of 1.00 

83.  (Ms).  Ships  and  Boats,  by  Bland 60 

83.  Book-keeping,  Haddon 60 

84.  Arithmetic,  by  Young .60 

84*.  Key  to  ditto 60 

85.  Equational  Arithmetic,  by  Hipsley 60 

86.  Algebra,  by  Haddon 80 

86*.  Key  to  ditto 60 

88.  Geometry.  Parti.  (Euclid,  Books  I.— IIL)  By  Law 60 


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89. Part  II.     (Euclid,  Books  IV.,  V.,  VI.,  XI.,  XII.)  By  Law.. .$0.60 

88.  89.  Geometry,  in  1  vol.  (Euclid's  Elements.) 1.00 

90.  Analytical  Geometry,  by  Hann  and  Young 80 

91.  Plane  Trigonometry,  by  Hann 60 

92.  Spherical  Trigonometry,  by  Hann 40 

91,  92,    bound  together 1.00 

93.  Mensuration  and  Measuring,  by  Baker 60 

96.  Astronomy,  by  Main.     Revised  by  W.  T.  Lynn 80 

97.  Statics  and  Dynamics,  by  Baker 60 

98.  Mechanism  and  Machines,  by  Baker  and  Nasmyth 1.00 

99.  Navigation  and  Nautical  Astronomy,  by  Young 1.00 

101.  Differential  Calculus,  by  Woolhouse 60 

102.  Integral  Calculus,  by  Cox 60 

106.  Ships'  Anchors,  by  Cotsell 

111.  Arches,  Piers  and  Buttresses,  by  Bland 60 

112.  Domestic  Medicines,  by  Gooding 80 

112*.  The  Management  of  Health,  by  Baird 40 

113.  On  the  Use  of  Field  Artillery,  by  H.  H.  Maxwell 

113.*  Memoir  on  Swords,  by  Col.  Marey 

116.  Acoustics  of  Public  Buildings,  by  Smith 60 

117.  Subterraneous  Surveying,  by  Fenwick  and  Baker 1.00 

118.  Civil  Engineering  in  North  America,  by  Stevenson 

127.  Architectural  Modeling,  by  Richardson 60 

128.  Vitruvius'  Architecture,   by  Gwilt 2.00 

130.  Grecian  Architecture,  by  Lord  Aberdeen 40 

128,  130,  in  1vol.  half-bound 2.40 

131.  Miller's,  Corn  Merchant's    and  Farmer's  Beady  Reckoner.     Revised 

by  Hutton 80 

132.  Dwelling  Houses,  Erection  of,  by  Brooks 1.00 

135.  Electro-metallurgy,  Watt 1.40 

136.  Arithmetic,  by  Haddon 60 

137.  Key  to  ditto 

138.  Telegraph,  Handbook  of,  by  Bond 

139.  Steam  Engine,  Theory  of,  by  Baker 00 

140.  Farming— Soils,  Manures  and  Crops,  by  Burn 80 

141.  Ditto        Outlines — Farming  Economy,  by  Burn 1.20 

142.  Ditto        Cattle,  Sheep  and  Horses,  by  Burn 1.00 

143.  Experimental  Essays,  by  C.  Towlinson 

145.  Farming,  Dairy,  Pigs,  and  Poultry,  by  Burn 80 

146.  Ditto        Sewage,  Irrigation,  &c.,  by  Burn 1.00 

140  to  146.  TheSvols.  in  1,  half-bound 4.80 

147.  The  Stepping  Stone  to  Arithmetic,  by  A.  Arman 

148.  Key  to  the  same 


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149.  Sails  and  Sailmaking,  by  Kipping $1.00 

150.  Logic,   by  Emmens 60 

151.  Handy  Book  on  the  Law  of  Friendly,  Industrial  and  Provident  Build- 

ing and  Loan  Societies,  by  A.  White 

153.  Locke  on  the  Understanding,  by  Emmens 60 

154.  General  Hints  to  Emigrants 

155.  Engineer's  Guide  to  the  Navies 

156.  Quantities  and  Measurements,  by  Beaton 60 

157.  Emigrant's  Guide  to  Natal,  by  Dr.  Mann 

158.  Slide  Rule  and  How  to  Use  it,  by  Hoare 1.00 

162.  Brass  Founder's  Manual,  by  W.  Graham 80 

163.  Law  of  Patents  for  Invention,  by  F.  W.  Campin 

164.  Modern  Workshop  Practice,    by  J.  G.  Winton.     Fourth  Edition,  re--' 

vised  and  enlarged , 1.40 

165.  Iron  and  Heat,  by  Armour 1.00 

166.  Power  in  Motion,  by  Armour 80 

167.  Iron  Bridges,  Girders,  &c.,  by  Campin 

168.  Drawing  and  Measuring  Instruments,  by  Heather 69 

169.  Optical  Instruments,  by  Heather 60 

170.  Surveying  and  Astronomical  Instruments,  by  Heather 60 

168,169,170.  The  three  parts  as  above  in  1  vol 1.80 

%*  The  above  form  an  enlargement  of  the  original  work,   ' '  Mathematical 

Instruments  "  (No.  32). 

171.  Engineering  Drawing,  by  John  Maxton 1.40 

172.  Mining  Tools,  by  William  Morgans 1.00 

172*.  Plates  to  ditto,  235  Engravings,  4to 1.80 

173.  Physical  Geology,  by  Portlock  and  Tate 80 

174.  Historical  Geology,  by  Ralph  Tate,  F.  G.  S 1.00 

173.  174.  Geology,  Portlock  and  Tate,  1  vol 1.80 

175.  Builder's  and  Contractor's  Price  Book 

176.  The  Metallurgy  of  Iron,  by  H.  Bauerman 2.00 

177.  Culture  of  Fruit  Trees,  by  Du  Breuil 1.40 

178.  Practical  Plane  Geometry,  by  J.  F.  Heather 80 

180.  Coal  and  Coal  Mining,  by  W.  W.  Smyth 1.40 

181.  Painting  (Fine  Art),  by  Gullick  and  Timbs 2.00 

182.  Carpentry  and  Joinery,  by  Tredgold  and  Tarn 1.40 

182*.  Atlas  of  35  plates  to  the  above 2.40 

183.  Animal  Physics,  by  Dr.  Lardner.     Parti 1.60 

184.  Ditto.     Part  II 1.20 

183,184.  Ditto.     In  1  Vol.     doth  boards 3.00 

185.  The  Complete  Measurer,  by  Richard  Horton 1.60 

186.  Grammar  of  Coloring,  by  Field,  Enlarged  by  Ellis  A.  Davidson,  with 

colored  plates 1.20 


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187.  Hints  to  Young    Architects,    by  G.    Wightwick,  Enlarged  by  G.  H. 

Guillaume . $1.40 

188.  House  Painting,  &c.,  by  Ellis  A.  Davidson 2.00 

189.  Practical  Bricklaying,  by  Adam  Hammond 60 

190.  Steam  and  the  Steam  Engine,  byD.  K.  Clark 1.40 

191.  Plumbing,   House    Drainage    and    Ventilation,    by  W.    P.  Buchan. 

Fifth  Edition,  Enlarged 1.40 

192.  Timber  Importers'  and  Builders'  Guide,  by  Grandy 80 

193.  Field  Fortification,  by  Major  W.  W.  Knollys 1.20 

194.  House  Manager,  by  an  Old  Housekeeper 1.40 

194,  112. 112*.  House  Book  (The).     Three  vols.  in  one,  half-bound 2.40 

196.  Compound  Interest  and  Annuities,  by  F.  Thoman 1.60 

197.  Roads  and  Streets,  by  Law  and  Clark 1.80 

198.  The  Sheep,  by  W.  C.  Spooner 1.40 

199.  The  Compendius  Calculator,  by  D.  O'Gorman,  revisod  by  C.  Norris....  1.00 

200.  Fuel,  byC.  W.  Williams  and  D.  K.  Clark 1.40 

201.  Kitchen  Gardening  made  Easy,  by  Glenny 60 

202.  Locomotive  Engines,  by  Dempsey,  with  additions  by  D.  K.  Clark 1.20 

203.  Sanitary  Work,  by  Charles  Slagg 1.20 

204.  Mathematical  and  Nautical  Tables,  with  Treatise  on  Logarithms,  by 

Law  and  Young 1.60 

204*.  Logarithms,  Treatise  on,  with  Tables,  by  Law,  from  the  above 1.20 

204&55.  Practical  Navigation,  in  1  vol.,  half-bound 2.80 

205.  Letter  Painting  Made  Easy,  by  J.  G.  Badenoch 60 

206.  A  Book  on  Building,  by  Sir  Edmund  Beckett 1.80 

207.  Farm  Management,  by  K.  Scott  Burn 1.00 

208.  Landed  Estates  Management,  by  E.  Scott  Burn 1.00 

207,  208,  Farm  and  Landed  Estates  Management,  by  E.  Scott  Burn,  in  1 

vol.,  half-bound 2.40 

209.  The  Tree  Planter  and  Plant  Propagator :  A  Practical  Manual,  by  Sam- 

uel Wood 80 

210.  The  Tree  Pruner,  by  Samuel  Wood 60 

209,  210.  The  Tree  Planter,  Propagator,  and  Pruner,  by  Samuel  Wood.    In 

1  vol.,  half-bound 1.40 

211.  The  Boilermaker's  Assistant,  by  Courtney 80 

212.  The  Construction  of  Gasworks,  by  S.  Hughes.     Seventh  Edition  by 

William  Eichards 2.20 

213.  Pioneer  Engineering,  by  Edward  Dobson,   C.  E 1.80 

214.  Slate  and  Slate  Quarrying,  byD.  C.  Davies 1.20 

215.  The  Goldsmith's  Handbook,  by  G.  E.  Gee 1.20 

216.  Materials  and  Construction,  by  F.  Campin 1.20 

217.  Sewing  Machinery,  by  J.  W.  Urquhart,  C.  E 80 

218.  Hay  and  Straw  Measurer,  by  John  Steele 80 


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219.  Civil  Engineering,  by  Law  and  Burnell,  with  Becent  Practice,  by  D. 

K.  Clarke,  M.  I.  C.  E $2.60 

221.  Measures,  Weights,  and  Moneys  of  All  Nations,  by  W.  S.  B.  Woolhouse. 

New  Edition 1.00 

222.  Suburban  Farming,  by  Prof .  Donaldson 

223.  Mechanical  Engineering,  by  F.  Camp  in,  C.  E 1.00 

224.  Coach  Building,  by  Jas.  W.  Burgess 1.00 

225.  The  Silversmith's  Handbook,  by  G.  E.  Gee 1.20 

215,  225.  The  Goldsmith's  and  Silversmith's  Complete  Handbook,  by  Gee. 

half-bound 2.80 

226.  The  Joints  used  by  Builders,  by  J.  W.   Christy 1.20 

227.  Mathematics  as  applied  to  the  Constructive  Arts,  by  F.  Campin,  C.  E.  1.20 

228.  The  Construction  of  Koofs,  by  E.  W.  Tarn 60 

229.  Elementary  Decoration,  by  J.  W.  Facey 80 

230.  Hand  Bailing  by  Geo.  Collings 1.00 

231.  Grafting  and  Buding,  by  C.  Baltet 1.00 

232.  Cottage  Gardening,  byE.  Hobday 60 

233.  Garden  Keceipts.     Edited  by  C.  W.  Quin 60 

234.  Market  and  Kitchen  Gardening,  by  C.  W.  Shaw 1.20 

235.  Practical  Organ-Building,  by  Dickson 1.00 

236.  Details  of  Machinery,  by  F.  Campin,  C.  E 1.20 

237.  The  Smithy  and  Forge,  by  Crane.     2d  Edition 1.00 

238.  Sheet  Metalworkers'  Guide,  by  Crane 60 

239.  Draining  and  Embanking,  by  Prof .  Scott 60 

240.  Irrigation  and  Water  Supply,  by  Prof.  Scott 60 

241.  Farm  Roads,  Fences  and  Gates,  by  Prof .  Scott 60 

242.  Farm  Buildings,  by  Prof.  Scott 80 

243.  Barn  Implements  and  Machines,  by  Prof. 'Scctt 80 

244.  Field  Implements  and  Machines,  by  Pros.  Scott 80 

245.  Agricultural  Surveying,  by  Prof .  Scott 60 

239  to  245.  TheTvols.  in  1,  half-bound 4.80 

246.  Dictionary  of  Painters,  by  P.  Daryl 1.00 

247.  Building  Estates,  by  Fowler  Maitland. 80 

248.  Portland  Cement  for  Users,  by  Faij  a 80 

249.  The  Hall-Marking  of  Jewelry,  by  Gee 1.20 

250.  Meat  Production,  by  John  Ewart 1.00 

251.  Steam  and  Machinery  Management,  by  M.  Powis  Bale,  C.  E 1.00 

232.  Brickwork,  a  Practical  Treatise,  by  F.  Walker.     2nd  Edition,  revised..     .60 
23,  189  &  252.  The  Practical  Brick  and  Tile  Book,  in  1  volume,  half-bound. 

253.  The  Timber  Merchant's  Freight  Book,  by  W.  Richardson  and  M.  P.  Bale, 

254.  The  Boilermaker's  Ready  Reckoner,  by  J.  Courtney,  revised  by  D. 

K.  Clark 1.60 

254  and  211  in  one  volume,  half  bound 2.80 


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256.  Stationary  Engine  Driving,  by  Michael  Reynolds $1.40 

257.  Practical  House  Decoration,  by  Facey 1.00 

229,  257.  House  Decoration,  by  Facey,  in  1  volume,  half -bound 2.00 

258.  Circular  Work  in  Carpentry,  by  Collings 1.00 

259.  Gas-Fitting,  by  John  Black 1.00 

260.  Iron  Bridges  of  Moderate  Span,  by  Hamilton  W.  Pendred 80 

261.  Shoring,  by  Geo.  H.  Blagrove 60 

262.  Boot  and  Shoemakmg,  by  J.  B.  Leno .80 

263.  Mechanical  Dentistry,  by  C.  Hunter '. 1.20 

264.  Mining  and   Quarrying,  by  J.  H.  Collins 60 

265.  Practical  Brick  Cutting  and  Setting,  by  Adam  Hammond. 60 

23,  189,  265  in  one  volume,  half  bound 2.40 

267.  The  Science  of  Building,  by  E.  W.  Tarn 1.40 

268.  The  Drainage  of  Lands,  Towns  and  Buildings,  by  G.  D.  Dempsey. 

Revised,  with  additions,  by  D.  K.  Clark.     2d  ed 1.80 

269.  Light;  an  Introduction  to  the  Science  of  Optics,  by  E.  W.  Tarn 60 

270.  Wood  Engraving,  by  W.  N.  Brown 60 

271.  Ventilation,  by  W.  P.  Buchan 1-40 

272.  Roof  Carpentry,  by  George  CoUings 80 

273.  The  Practical  Plasterer,  by  W.  Kemp 8C 

274.  Elementary  Marine  Engineering,  by  J.  S.  Brewer 60 

275.  Laundry  Management 80 

276.  Cement,  Pastes,  Glues  and  Gums,  by  H.  C.  Standage 80 

277.  Fuels  ;  Their  Analysis  and  Valuation,  by  E.  J.  Phillips 80 

278.  Model  Locomotive  Engineer,  Fireman,  &c.,  by  M.  Reynolds 1.40 

279.  Constructional  Iron  and  Steel  V7ork,  by  F.  Campin 1. 40 

280.  Iron  and  Steel  Bridges  and  Viaducts,  by  F.  Campin 1.40 

281.  French  Polishing  and  Enamelling,  by  R.  Bitmead 60 

282.  Electric  Lighting,  by  A.  A.  C.  Swinton 60 


